Bowlers losing power? They've done something wrong! (7)
I believe the answer is:
sinners
'they've done something wrong' is the definition.
I can't judge whether this defines the answer.
'bowlers losing power?' is the wordplay.
'bowlers' becomes 'spinners' (spinner is a type of cricket bowler).
'losing' is a deletion indicator.
'power?' becomes 'p'.
'spinners' with 'p' taken away is 'SINNERS'.
Can you help me to learn more?
(Other definitions for sinners that I've seen before include "criminals" , "Transgressors of divine law" .)