Hard-up criminal in seclusion (6)
I believe the answer is:
purdah
'seclusion' is the definition.
(I've seen this before)
'hard-up criminal' is the wordplay.
'criminal' indicates anagramming the letters.
'hard'+'up'='hardup'
'hardup' anagrammed gives 'PURDAH'.
'in' is the link.
(Other definitions for purdah that I've seen before include "Hindu or Muslim seclusion of women" , "Screening curtain; seclusion" , "Seclusion of women as religious practice" , "Hindu system of keeping women from sight of men" , "Women's seclusion" .)