Characters that could be hard up in social isolation (6)
I believe the answer is:
purdah
'social isolation' is the definition.
(I've seen this before)
'characters that could be hard up' is the wordplay.
'characters that could be' is an anagram indicator (letters or characters rearranged).
'hard'+'up'='hardup'
'hardup' is an anagram of 'PURDAH'.
'in' is the link.
(Other definitions for purdah that I've seen before include "Period of seclusion" , "State of social isolation" , "Muslim and Hindu custom of keeping women secluded" , "Eastern tradition of keeping women secluded" , "System in Muslim communities of keeping women from the sight of men" .)