Locks most important it's said (4)
I believe the answer is:
mane
'locks' is the definition.
(I've seen this in other clues)
'most important it's said' is the wordplay.
'most important' becomes 'main' (main can mean the most important or major).
'it's said' shows a homophone (sound like).
'main' is a homophone of 'MANE'.
(Other definitions for mane that I've seen before include "Long shaggy hair" , "Animal's neck hair" , "Name for hair on horse's neck" , "Animal neck-hair" , "Long flowing hair" .)