Settle a clue (6)
I believe the answer is:
alight
'settle' is the definition.
(I've seen this before)
'a clue' is the wordplay.
'clue' becomes 'light'.
'a'+'light'='ALIGHT'
(Other definitions for alight that I've seen before include "Leave a vehicle - burning" , "Descend, from a bus or train say" , "Touch down" , "Small restaurant" , "Come down - on fire" .)