Gander expressed anger (4)
I believe the answer is:
peek
'gander' is the definition.
(thesaurus)
'expressed anger' is the wordplay.
'expressed' indicates a 'sounds like' (homophone) clue.
'anger' becomes 'pique' (piquing is a kind of angering).
'pique' sounds like 'PEEK'.
(Other definitions for peek that I've seen before include "Sly look, peep" , "Repeatedly look like this" , "Furtive glance" , "Glimpse" , "Take brief or surreptitious look" .)