Relative with a name for being filthy (7)
I believe the answer is:
unclean
'being filthy' is the definition.
(similar in meaning)
'relative with a name' is the wordplay.
'relative' becomes 'uncle' (uncle is a kind of relative).
'with' is a charade indicator (letters next to each other).
'name' becomes 'n' (common abbreviation e.g. on forms).
'uncle'+'a'+'n'='UNCLEAN'
'for' is the link.
(Other definitions for unclean that I've seen before include "Foul" , "Soiled like an uncle" , "Infected" , "Dirty or unwashed" , "Contaminated" .)