Paper with unfinished petition, for instance (7)
I believe the answer is:
example
'for instance' is the definition.
(synonyms)
'paper with unfinished petition' is the wordplay.
'paper' becomes 'exam' (exam paper).
'with' is a charade indicator (letters next to each other).
'unfinished' means to remove the last letter.
'petition' becomes 'plea' (petition can mean to plea or beg).
'plea' with its final letter removed is 'ple'.
'exam'+'ple'='EXAMPLE'
(Other definitions for example that I've seen before include "Illustration or model" , "Instance or illustration" , "Illustration or paradigm" , "Ideal - specimen" , "Standard" .)