Suitable returns following argument (4)
I believe the answer is:
tiff
'argument' is the definition.
(thesaurus)
'suitable returns following' is the wordplay.
'suitable' becomes 'fit' ('fit' can be similar in meaning to 'suitable').
'returns' is a reversal indicator.
'following' becomes 'f' (used when citing page numbers etc).
'fit' backwards is 'tif'.
'tif'+'f'='TIFF'
(Other definitions for tiff that I've seen before include "Hard to lose opening argument" , "pet" , "Slight argument" , "(Lovers') quarrel" , "Petty argument" .)