Dagger gutted Helen, a deity (7)
I believe the answer is:
krishna
'deity' is the definition.
(Krishna is an example)
'dagger gutted helen a' is the wordplay.
'dagger' becomes 'kris' (I've seen this before).
'gutted' means to remove the middle letters (to gut something is to remove its insides).
'helen' with its middle removed is 'hn'.
'kris'+'hn'+'a'='KRISHNA'
(Other definitions for krishna that I've seen before include "Most important avatar of Vishnu" , "Hindu deity - Sikh ran (anag)" , "Hare ..., religious sect based on Vedic scriptures" , "Hare ..., religious sect whose devotees wear saffron robes" , "divine figure" .)