Tough guy dined out with grand trousers (9)
I believe the answer is:
demanding
'tough' is the definition.
(thesaurus)
'guy dined out with grand trousers' is the wordplay.
'guy' becomes 'man ' (guy can informally mean a man).
'out with' indicates anagramming the letters (out can mean wrong or inaccurate).
'grand' becomes 'G' (synonyms).
'trousers' means one lot of letters goes inside another (to trouser can mean to steal or take).
'dined' mixed up with 'g' makes 'deding'.
'man' put into 'deding' is 'DEMANDING'.
(Other definitions for demanding that I've seen before include "Requesting" , "Stringent" , "Requiring much effort" , "Exigent" .)