Jailer fitting gold key first (6)
I believe the answer is:
captor
'jailer' is the definition.
(I've seen this before)
'fitting gold key first' is the wordplay.
I cannot quite understand how this works, but
'fitting' could be 'apt' (I've seen this before) and 'apt' is found in the answer.
'gold' could be 'or' ('or' is the heraldic name for gold) and 'or' is located in the answer.
'key' could be 'c' (musical key) and 'c' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for captor that I've seen before include "One who takes a prisoner" , "kidnapper, perhaps" , "Guard" , "Holder of a prisoner" , "Top car (anag) -- jailer" .)