Be wildly excited putting pineapple to mouth (2,7)
I believe the answer is:
go bananas
'be wildly excited' is the definition.
'pineapple to mouth' is the wordplay.
'pineapple' becomes 'ananas' ('ananas' can be a synonym of 'pineapple').
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'mouth' becomes 'gob' (I've seen this before).
'ananas' put after 'gob' is 'GO BANANAS'.
'putting' acts as a link.
(Other definitions for go bananas that I've seen before include "Get very annoyed" , "Become mad or furious" , "Lose one's cool" , "Flip one's lid (sl.)" , "Freak out" .)