Old king holding on for Churchill, say (7)
I believe the answer is:
college
'churchill say' is the definition.
(Cambridge college)
'old king holding on' is the wordplay.
'old king' becomes 'cole'.
'holding' indicates putting letters inside.
'on' becomes 'leg' (cricket term, fielding positions).
'cole' placed around 'leg' is 'COLLEGE'.
'for' is the link.
(Other definitions for college that I've seen before include "Educational institution" , "University establishment" , "eg Eton" , "Balliol, perhaps?" , "Eg, Magdalen, Balliol" .)