Makes breathless male separate aboard steamer (8)
I believe the answer is:
smothers
'makes breathless' is the definition.
(I've seen this before)
'male separate aboard steamer' is the wordplay.
'male' becomes 'm' (common abbreviation).
'separate' becomes 'other' ('other' is associated in meaning with 'separate'**).
'aboard' indicates putting letters inside.
'steamer' becomes 'ss'.
'm'+'other'='mother'
'mother' going into 'ss' is 'SMOTHERS'.
(Other definitions for smothers that I've seen before include "envelops" , "Suffocates, stifles" , "Makes breathless" .)