Argument suitable to be backed with force (4)
I believe the answer is:
tiff
'argument' is the definition.
(I know that tiff is a type of argument)
'suitable to be backed with force' is the wordplay.
'suitable' becomes 'fit' (similar in meaning).
'to be backed' is a reversal indicator.
'with' is a charade indicator (letters next to each other).
'force' becomes 'f' (abbreviation in physics e.g. f=ma).
'fit' in reverse letter order is 'tif'.
'tif'+'f'='TIFF'
(Other definitions for tiff that I've seen before include "dispute" , "Minor argument" , "Lovers' row" , "Petty squabble" , "A spat or small row" .)