Flatten target, then take a nap (8)
I believe the answer is:
bulldoze
'flatten' is the definition.
(I've seen this before)
'target then take a nap' is the wordplay.
'target' becomes 'bull' (centre of a target).
'then' is a charade indicator (letters next to each other).
'take a nap' becomes 'doze'.
'bull'+'doze'='BULLDOZE'
(Other definitions for bulldoze that I've seen before include "Demolish; ride roughshod over" , "Flatten with a large powerful tractor" , "Railroad" , "Completely flatten" , "Mechanically flatten" .)