Search for, on the crest (4)
I believe the answer is:
comb
This could be a double definition.
'search for' is the first definition.
'comb' can be an answer for 'search' (combing is a kind of searching). I'm unsure of the 'for' bit.
'the crest' is the second definition.
(comb is a kind of crest)
'on' acts as a link.
Can you help me to learn more?
(Other definitions for comb that I've seen before include "Implement with teeth" , "Rummage through" , "Implement for grooming hair" , "Toothed instrument" , "Arrange" .)