Guide or prophet out to start trouble (5)
I believe the answer is:
steer
'guide' is the definition.
(I know that guide can be written as steer)
'prophet out to start trouble' is the wordplay.
'prophet' becomes 'seer' (both can mean someone who tells the future).
'out' is an insertion indicator.
'to start' suggests taking the first letters.
The initial letter of 'trouble' is 't'.
'seer' placed around 't' is 'STEER'.
'or' is the link.
(Other definitions for steer that I've seen before include "Reset so as to direct" , "Guide (a ship, car, etc)" , "Exercise control" , "member of herd" , "farm animal" .)