Tip off pro: create conflict between opponents (8)
I believe the answer is:
Here is my best explanation:
'tip off' is the definition.
(I've seen this before)
'pro create conflict between opponents' is the wordplay.
'pro' becomes 'for' (I've seen this before).
'create' says to put letters next to each other.
'conflict' becomes 'war' (war is a kind of conflict).
'between' indicates putting letters inside.
'opponents' becomes 'en' (I've seen this in other clues).
'war' inserted into 'en' is 'ewarn'.