Stir up trouble at gate 1 (7)
I believe the answer is:
agitate
'stir up' is the definition.
('agitate' can be a synonym of 'stir up')
'trouble at gate 1' is the wordplay.
'trouble' indicates an anagram.
'1' becomes 'i' (roman numeral).
'at'+'gate'+'i'='atgatei'
'atgatei' with letters rearranged gives 'AGITATE'.
(Other definitions for agitate that I've seen before include "Stir (up public opinion?)" , "Fluster" , "Make nervous; stir" , "Upset, disturb the surface of" , "Disturb or stir up" .)