Colour of bream at sea (5)
I believe the answer is:
amber
'colour' is the definition.
(amber is a kind of colour)
'bream at sea' is the wordplay.
'at sea' indicates an anagram.
'bream' anagrammed gives 'AMBER'.
'of' is the link.
(Other definitions for amber that I've seen before include "Neither red nor green?" , "Prepare-to-stop signal" , "Fossilised resin used in jewellery" , "Girl" , "Deep yellow" .)