Provides backing musicians but no leader (7)
I believe the answer is:
assists
'provides backing' is the definition.
'assists' can be an answer for 'provides' (I've seen this before). I am unsure of the 'backing' bit.
'musicians but no leader' is the wordplay.
'musicians' becomes 'bassists' (I've seen this before).
'but no leader' means to remove the first letter.
'bassists' with its initial letter taken away is 'ASSISTS'.
Can you help me to learn more?
(Other definitions for assists that I've seen before include "Contributes to success" , "Lends a hand" , "Provides" , "Helps or waits on" , "Aids" .)