Invalid pleads for a change (6)
I believe the answer is:
lapsed
'invalid' is the definition.
(I've seen this before)
'pleads for a change' is the wordplay.
'for a change' is an anagram indicator.
'pleads' is an anagram of 'LAPSED'.
(Other definitions for lapsed that I've seen before include "No longer active or practising" , "Expired over pedals" , "Fallen away from the faith" , "Ceased to practise faith" , "Out of date" .)