Catch name? Boatman (3)
I believe the answer is:
nab
'catch' is the definition.
(nab can mean to capture or arrest)
'name? boatman' is the wordplay.
'name?' becomes 'n' (common abbreviation e.g. on forms).
'boatman' becomes 'ab' (abbreviation for able seaman).
'n'+'ab'='NAB'
(Other definitions for nab that I've seen before include "Pinch" , "Run in" , "Take" , "Capture (slang)" , "Apprehend" .)