Thanks for all the entries. Many had the desirable qualities of soundness and an apt surface. I liked darla's duo @18 and 19, mattrom's choice of evening reading @22, buddy @3 (if only expenses instead of expense could have been worked into it!). This brings me to my top 3:
Bronze: tyke51 @6
Starts to convert organic matter after soil improver (7)
Silver: jono @17 making a rare application to join the Bad Boys' Club:
Poms frolicking in bed? It might encourage growth of sticky willy! (7)
Gold: mattrom @8 reminding us of that useful Scrabble two-letter word ST as an alternative to SH. The 'compo' slang was new to me but absolutely sound.
Make a pile quietly on payment for injuries (7)
Congratulations, mattrom. Here is your instructional prize. I am not much of a gardener and my attempt at a heap turned out far too slimy.
https://youtu.be/9zvFresyPmA