Canned eels can have a purifying effect (7)
I believe the answer is:
cleanse
'a purifying effect' is the definition.
Although both the answer and definition are verbs in their base form, I cannot see how one could define the other.
'canned eels can' is the wordplay.
'canned' is an anagram indicator (canned can mean drunk).
'eels'+'can'='eelscan'
'eelscan' anagrammed gives 'CLEANSE'.
'have' acts as a link.
Can you help me to learn more?
(Other definitions for cleanse that I've seen before include "absolve from sin" , "Make free from dirt" , "purify from sin" , "give absolution" , "Thoroughly remove dirt from" .)