Rubbish! As if fly could misrepresent? (7)
I believe the answer is:
falsify
'misrepresent?' is the definition.
(synonyms)
'rubbish as if fly' is the wordplay.
'rubbish' indicates anagramming the letters (a poor quality or rubbish spelling of the letters).
'as'+'if'+'fly'='asiffly'
'asiffly' with letters rearranged gives 'FALSIFY'.
'could' acts as a link.
(Other definitions for falsify that I've seen before include "Cook - distort" , "Counterfeit" , "Alter so as to mislead" , "Forge; misrepresent" , "Alter in order to deceive" .)