Also after leader of backing group (4)
I believe the answer is:
band
'group' is the definition.
(band is a kind of group)
'also after leader of backing' is the wordplay.
'also' becomes 'and' (I've seen this before).
'after' says to put letters next to each other.
'leader of' suggests taking the first letters.
The first letter of 'backing' is 'b'.
'and' after 'b' is 'BAND'.
(Other definitions for band that I've seen before include "Musicians - circle" , "Ring or musical group (4)" , "A collection of musicians in ring" , "company" , "Pop group, perhaps" .)