See clan destroyed in purge (7)
I believe the answer is:
cleanse
'purge' is the definition.
(I've seen this before)
'see clan destroyed' is the wordplay.
'destroyed' indicates an anagram.
'see'+'clan'='seeclan'
'seeclan' is an anagram of 'CLEANSE'.
'in' acts as a link.
(Other definitions for cleanse that I've seen before include "clear of muck" , "subject to purification" , "Make spotless" , "carry out purification" , "give absolution" .)