Gold corporation down at last for three months of the year (6)
I believe the answer is:
autumn
'three months of the year' is the definition.
'gold corporation down at last' is the wordplay.
'gold' becomes 'au' ('Au' can be a synonym of 'gold').
'corporation' becomes 'tum' (I've seen this before).
'at last' says to take the final letters.
The final letter of 'down' is 'n'.
'au'+'tum'+'n'='AUTUMN'
'for' is the link.
(Other definitions for autumn that I've seen before include "1 Season of mists and mellow fruitfulness" , "Time of year" , "addressed by Keats" , "'O wild West Wind, thou breath of . . . . . . 's being' (Shelley)" , "Fall in the US" .)