Blimey! Free gold in passage (8)
I believe the answer is:
corridor
'passage' is the definition.
(corridor is a kind of passage)
'blimey free gold' is the wordplay.
'blimey' becomes 'cor' (I've seen this in other clues).
'free' becomes 'rid' ('rid' can be a synonym of 'free').
'gold' becomes 'or' ('or' is the heraldic name for gold).
'cor'+'rid'+'or'='CORRIDOR'
'in' acts as a link.
(Other definitions for corridor that I've seen before include "Indoor passageway" , "Enclosed passageway wtih rooms off" , "way through" , "Passageway between rows of offices" , "Passage (of power?)" .)