Fixes up favourite for scrap (7)
I believe the answer is:
snippet
'scrap' is the definition.
(thesaurus)
'fixes up favourite' is the wordplay.
'fixes' becomes 'pins' (pinning is a kind of fixing).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'favourite' becomes 'pet' ('pet' can be a synonym of 'favourite').
'pins' written backwards gives 'snip'.
'snip'+'pet'='SNIPPET'
'for' acts as a link.
(Other definitions for snippet that I've seen before include "A cutting" , "piece of information" , "Bit (of info?)" , "Scrap (of information, news etc)" , "A small piece cut off" .)