Motive for arson, maybe, out East (6)
I believe the answer is:
reason
'motive' is the definition.
(reason is a kind of motive)
'arson maybe out east' is the wordplay.
'maybe' indicates anagramming the letters.
'out' means one lot of letters goes inside another.
'east' becomes 'e' ('E' can be a synonym of 'east').
'arson' anagrammed gives 'rason'.
'rason' placed around 'e' is 'REASON'.
'for' is the link.
(Other definitions for reason that I've seen before include "Sanity and logic" , "Motive; argue" , "Cause, justification" , "Cause; think logically" , "Cause - logic" .)