Lifeless hair: you can do nothing with it! (8)
I believe the answer is:
deadlock
'you can do nothing with it' is the definition.
(situation with no obvious resolution)
'lifeless hair' is the wordplay.
'lifeless' becomes 'dead' (similar in meaning).
'hair' becomes 'lock' (lock is a kind of hair).
'dead'+'lock'='DEADLOCK'
(Other definitions for deadlock that I've seen before include "Situation from which no progress can be made" , "Stalemate - impasse" , "Something opened by a key - stalemate" , "Intractable problem" , "Log jam" .)