27 across
Undercover
cop,
perhaps
with
retro-style
ponytail
(5)
Undercover cop, perhaps with retro-style ponytail (5)
hints
0
checks
0
hints
The definition is at the beginning of the clue.
How the clue works
The definition is Undercover cop, perhaps, since a decoy is someone used as a lure, and a police officer working undercover would fit that bill. For the wordplay, take DECO, the retro style (think Art Deco), and tack on Y, the tail of "pony" (a "ponytail", after all). Put them together and you've got your answer.