Foolishly queries tip as fringe benefit (10)
I believe the answer is:
perquisite
'fringe benefit' is the definition.
(synonyms)
'foolishly queries tip' is the wordplay.
'foolishly' indicates anagramming the letters.
'queries'+'tip'='queriestip'
'queriestip' anagrammed gives 'PERQUISITE'.
'as' is the link.
(Other definitions for perquisite that I've seen before include "Extra benefit" , "incidental benefit" .)