To evaluate a paper is tricky. (8)
I believe the answer is:
appraise
'to evaluate' is the definition.
(to appraise is to evaluate or assess)
'a paper is tricky' is the wordplay.
'tricky' indicates anagramming the letters.
'paper'+'is'='paperis'
'paperis' is an anagram of 'ppraise'.
'a'+'ppraise'='APPRAISE'
(Other definitions for appraise that I've seen before include "Assess the value/quality of (something)" , "Tip off" , "Assess, set a price on" , "Make assessment of value or quality" , "survey?" .)