Family member doesn't start to let loose (5)
I believe the answer is:
untie
'let loose' is the definition.
(I've seen this in another clue)
'family member doesn't start' is the wordplay.
'family member' becomes 'auntie' (I've seen this before).
'doesn't start' means to remove the first letter.
'auntie' with its initial letter removed is 'UNTIE'.
'to' is the link.
(Other definitions for untie that I've seen before include "Undo a knot" , "Release (knots)" , "Let loose" , "Set free" , "Loose bonds" .)