Time and motivation for serious crime (7)
I believe the answer is:
treason
'serious crime' is the definition.
(I've seen this before)
'time and motivation' is the wordplay.
'time' becomes 't'.
'and' means one lot of letters go next to another.
'motivation' becomes 'reason' (reason is a kind of motivation).
't'+'reason'='TREASON'
'for' is the link.
(Other definitions for treason that I've seen before include "Criminal attempt to overthrow a government" , "Crime of treachery against the state" , "Offence against state" , "Disloyalty (to one's country)" , "Senator (anag)" .)