Cryptic crossword No 4,029

Across

1. Altering autonomously is key (8)
2. Replenish stream (4)
3. Sweetheart has nothing in the sack (7)
4. Component of surface to need solvent (7)
5. Friendly type (4)
6. Cram under done starters into hole (5)
7. Start to enhancement found in the old you (4)
8. Quick set (4)
9. Fastener rotating in container (3)
10. Feature of Jesus, his production of fish (5)
11. Reign with king, able to measure up (5)
12. Talk about satchel (3)
13. The best ever butter (4)
14. Steals from reversal of restriction on spades (4)
15. Announcement system with no time results in bug (5)
16. Cream, unconventional cure (4)
17. Fasteners from satchel adjusted (7)
18. After miles, river joins railway - a place full of rodents (7)
19. Get rid of out-building (4)
20. Jab containing enervating drug always starts causing sleep (8)

Down

1. Fibres in disarray, only beginning to normalise (5)
2. Diplomatic messenger without love begets jealousy (4)
3. Defensive position about lack of confidence (7)
4. Christmas back with social worker trusted (5,2)
5. New leaf jumper (4)
6. Stand around at front of hotel for long period of time (5)
7. Start grinding Gneiss around the beginning of evening (7)
8. Cook prepared kebab without boiling first (4)
9. Origin in giant rat speeding backwards (5)
10. Saving freely without a crude gesture (1,4)
11. Punch everything noisy (3)
12. Historic bath regularly found in sepia (3)
13. Essentially, bug's inside is disgusting (7)
14. See guns obliquely, coming to classes (7)
15. Untidy bedroom swept (7)
16. Are you near red? (4)
17. Composer of organ music holds first of tocattas: it's a lot (5)
18. Wholesome family, full of energy (5)
19. Among Spanish oddballs, with covered feet (4)
20. Only fair (4)