I set nobles up, it’s pretended (10)
I believe the answer is:
ostensible
'pretended' is the definition.
(thesaurus)
'i set nobles up' is the wordplay.
'up' indicates an anagram (letters get chucked up).
'i'+'set'+'nobles'='isetnobles'
'isetnobles' is an anagram of 'OSTENSIBLE'.
'it's' acts as a link.
(Other definitions for ostensible that I've seen before include "Apparent" , "Supposed" , "Apparently true" , "Manifest" , "Professed" .)