Especially for Mamya 8) ...
To help you decide in future:- the clue will break into (1) a definition of the solution and (2) the wordplay (here the 'sounds like' bit).
First question - is the 'sounds like' indicator at one end of the clue? If so, that end must be the wordplay part.
In "Reported witnessed incident', the 'sounds like' indicator is at the start, it's the 'witnessed' ('seen') that's being heard, and the answer is SCENE ('incident').
If, though, it were 'Witnessed incident that's been reported', with the 'sounds like' indicator at the end, then it's the 'scene' that's being heard to produce SEEN. So with 'Fine cut for commentators', the 'shear' is being heard and the answer is SHEER.
What about 'Witnessed reported incident', with the indicator right in the middle? Then you can't tell (it would be an unfair clue, although if the lengths of the two homophones were different, as with SEEN/SCENE, then the length of the entry would tell you the answer).
But if there is a 'link word' then it's ok - in 'Witnessed results from reported incident', the linking 'results from' separates the definition ('witnessed') from the wordplay ('reported incident'), so here it is the 'scene' being reported and the answer is SEEN.
In this Daily Mail clue ['Drive onto shore, say, for tree'], 'for' is the separating link word, which means that the 'say' indicator belongs unequivocally to the 'Drive onto shore', so the solution is BEECH.