Company with Marx Brothers' heads for crest (4)
I believe the answer is:
comb
'for crest' is the definition.
(comb is a kind of crest)
'company with marx brothers' heads' is the wordplay.
'company' becomes 'co' (abbreviation).
'with' is a charade indicator (letters next to each other).
'heads' says to take the initial letters.
The first letters of 'marx brothers' is 'mb'.
'co'+'mb'='COMB'
(Other definitions for comb that I've seen before include "Toothed implement - search (the area)" , "Crest on the head of some birds" , "business storage unit" , "Device with teeth - store for honey" , "Common hair tidier" .)