Flower finished in loch first (5)
I believe the answer is:
lupin
'flower' is the definition.
(I've seen this before)
'finished in loch first' is the wordplay.
'finished' becomes 'up' ('up' can be similar in meaning to 'finished').
'loch' becomes 'l'.
'first' is a charade indicator (letters next to each other).
'up'+'in'='upin'
'upin' put after 'l' is 'LUPIN'.
(Other definitions for lupin that I've seen before include "Plant called after wolf" , "Tall-spiked flower" , "Flowering plant" , "Fodder plant" , "Nil up in this flower" .)