Sailor dismissed roughly (5)
I believe the answer is:
about
'roughly' is the definition.
('about' can be a synonym of 'roughly')
'sailor dismissed' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'dismissed' becomes 'out' (I've seen this before).
'ab'+'out'='ABOUT'
(Other definitions for about that I've seen before include "In conection with, all around" , "Concerning or around" , "'All - - Eve' (film)" , "Concerning (something)" , "Nearly" .)