Group losing leader with depression (4)
I believe the answer is:
lump
'group' is the definition.
(lump is a kind of group)
'losing leader with depression' is the wordplay.
'leader' suggests taking the first letters.
'with' is a charade indicator (letters next to each other).
'depression' becomes 'ump' (I can't justify this - if you can you should believe this answer much more).
The first letter of 'losing' is 'l'.
'l'+'ump'='LUMP'
(Other definitions for lump that I've seen before include "Irregularly shaped piece" , "Small shapeless mass" , "Plum in a compact shapeless mass" , "Large piece without definite shape" , "Chunk, clod, nodule" .)