Single man coming in punctually (2,4)
I believe the answer is:
on time
'punctually' is the definition.
(I've seen this in another clue)
'single man coming in' is the wordplay.
'single' becomes 'one' (a single thing - only one).
'man' becomes 'tim' (short for Timothy).
'coming in' indicates putting letters inside.
'one' going around 'tim' is 'ON TIME'.
(Other definitions for on time that I've seen before include "Arriving when due" , "as expected" , "Not running late" , "promptly" , "Punctual, not late" .)