Revealing garment, quick way to dress topless crime writer (7)

'revealing garment' is the definition.
(bikini worn by a man)

'quick way to dress topless crime writer' is the wordplay.
'quick way' becomes 'mi' (resembles M1, English motorway).
'to dress' means one lot of letters goes inside another (inserted letters are dressed in another word).
'topless' means to remove the first letter.
'crime writer' becomes 'rankin' (Ian Rankin).
'rankin' with its initial letter taken away is 'ankin'.
'mi' going around 'ankin' is 'MANKINI'.