Short sailor put out crossing river (6)
I believe the answer is:
abrupt
'short' is the definition.
(I've seen this in another clue)
'sailor put out crossing river' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'crossing' indicates putting letters inside.
'river' becomes 'r' (abbreviation for river).
'put' with letters rearranged gives 'upt'.
'upt' enclosing 'r' is 'rupt'.
'ab'+'rupt'='ABRUPT'
(Other definitions for abrupt that I've seen before include "Offhand" , "Brusque, curt" , "Short and brusque" , "Rough and quick" , "Sudden - blunt" .)