Colour of bream at sea (5)
I believe the answer is:
Here is my best explanation:
'colour' is the definition.
(amber is a kind of colour)
'bream at sea' is the subsidiary indication.
'at sea' is an anagram indicator.
'bream' anagrammed gives 'amber'.
'of' is the link.
(Other definitions for amber that I've seen before include "Colour between red and green?", "Honey-yellow colour", "Middle light", "Fossil resin - bream (anag)", "Fossil resin used in jewellery", "Traffic-light between red and green", "Bream (anag.)", "Yellowish fossilised resin", "Fossilised resin used in jewellery" and "Yellow-brown colour as of bream".)