Needs brute to loosen bonds (10)
I believe the answer is:
debentures
'bonds' is the definition.
(debenture is a kind of bond)
'needs brute to loosen' is the wordplay.
'to loosen' indicates anagramming the letters (I've seen 'loosened' mean this).
'needs'+'brute'='needsbrute'
'needsbrute' anagrammed gives 'DEBENTURES'.
(Other definitions for debentures that I've seen before include "Shares" , "Bonds" .)