English politician gatecrashes trial, creating a commotion (7)
I believe the answer is:
'a commotion' is the definition.
(I know that tempest is a type of commotion)
'english politician gatecrashes trial' is the wordplay.
'english' becomes 'e' (abbreviation).
'politician' becomes 'MP' (Member of Parliament).
'gatecrashes' is an insertion indicator (inserted letters gatecrash their way into the word).
'trial' becomes 'test' (synonyms).
'emp' placed inside 'test' is 'TEMPEST'.
'creating' acts as a link.
(Other definitions for tempest that I've seen before include "terrible blow" , "Violent windy storm" , "A violent storm like Shakespeare's" , "Shakespeare's 5" , "Outburst" .)