Relative, after losing heart, has broken free (7)
I believe the answer is:
unleash
'free' is the definition.
(I've seen this before)
'relative after losing heart has broken' is the wordplay.
'relative' becomes 'uncle' (uncle is a kind of relative).
'after losing heart' says to hollow out the word (remove centre letters).
'broken' indicates an anagram.
'uncle' with its centre taken out is 'unle'.
'has' with letters rearranged gives 'ash'.
'unle'+'ash'='UNLEASH'
(Other definitions for unleash that I've seen before include "Let free" , "Let loose" , "Let go" , "Flee from restraint, allow to pursue like dog" , "Shun ale to free from restraint" .)