Lifeless hair? There’s no spring in it (8)
I believe the answer is:
deadlock
'there's no spring in it' is the definition.
(lock that doesn't contain a spring)
'lifeless hair?' is the wordplay.
'lifeless' becomes 'dead' (synonyms).
'hair?' becomes 'lock' (lock is a kind of hair).
'dead'+'lock'='DEADLOCK'
(Other definitions for deadlock that I've seen before include "Log jam" , "Impasse, standoff" , "Stalemate - it requires a key to open" , "Stalemate - impasse" , "Standstill" .)