Support from British stock (5)
I believe the answer is:
brace
'support' is the definition.
(brace is a kind of support)
'british stock' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'stock' becomes 'race' (I've seen this before).
'b'+'race'='BRACE'
'from' is the link.
(Other definitions for brace that I've seen before include "Pair - supporting beam" , "Secure" , "Strengthen; pair" , "Pair of game-birds" , "Pair - wood-boring tool" .)