Bishop introducing different trouble (6)
I believe the answer is:
bother
'trouble' is the definition.
(I know that bother is a kind of agitate)
'bishop introducing different' is the wordplay.
'introducing' says to take the initial letters (I've seen 'introduced' mean this).
'different' becomes 'other' (similar in meaning).
The first letter of 'bishop' is 'b'.
'b'+'other'='BOTHER'
(Other definitions for bother that I've seen before include "Annoy, disturb" , "Take the trouble to do something" , "Fuss, ado" , "Discommode, annoy" , "Annoy or pester" .)