Sun hack is not to remove the halo (7)

I believe the answer is:

unsaint

'remove the halo' is the definition.
(saints are normally depicted with halos)

'sun hack is not' is the wordplay.
'hack' indicates an anagram (I've seen 'hacking' mean this).
'is not' becomes 'aint' (I've seen this before).
'sun' with letters rearranged gives 'uns'.
'uns'+'aint'='UNSAINT'

'to' is the link.

I've seen this clue in The Guardian.

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