Warning - not if loyal heart mixed gin (9)

I believe the answer is:

notifying

'warning' is the definition.
(thesaurus)

'not if loyal heart mixed gin' is the wordplay.
'heart' means to look at the middle letters.
'mixed' is an anagram indicator.
The middle letter of 'loyal' is 'y'.
'gin' anagrammed gives 'ing'.
'not'+'if'+'y'+'ing'='NOTIFYING'

(Another definition for notifying that I've seen is " Officially informing (someone)".)

I've seen this clue in the Sydney Morning Herald.

Want a hint initially instead of a full solution? Install my app