Copier under pressure in exam (5)
I believe the answer is:
paper
'exam' is the definition.
'copier under pressure' is the wordplay.
'copier' becomes 'aper' (ape can mean to copy or imitate).
'under' says to put letters next to each other.
'pressure' becomes 'p' (abbreviation).
'aper' after 'p' is 'PAPER'.
'in' is the link.
(Other definitions for paper that I've seen before include "Dissertation" , "News medium" , "Short essay" , "It's made from wood pulp generally" , "Government report" .)