Popular elected government briefly upset with EU (2,5)
I believe the answer is:
in vogue
'popular' is the definition.
(thesaurus)
'elected government briefly upset with eu' is the wordplay.
'elected' becomes 'in' (in government).
'government briefly' becomes 'gov' ('briefly' suggests a short form).
'upset' says the letters should be written backwards.
'with' is a charade indicator (letters next to each other).
'eu' becomes 'ue' (I can't justify this - if you can you should believe this answer much more).
'gov' reversed gives 'vog'.
'in'+'vog'+'ue'='IN VOGUE'
Can you help me to learn more?
(Other definitions for in vogue that I've seen before include "'In the current fashion or style (2,5)'" , "A la mode, fashionable" , "Currently fashionable" .)