Suppose rep upset nurse (7)
I believe the answer is:
pretend
'suppose' is the definition.
(I've seen this before)
'rep upset nurse' is the wordplay.
'upset' is an anagram indicator.
'nurse' becomes 'tend' (tend can mean to nurse or look after).
'rep' with letters rearranged gives 'pre'.
'pre'+'tend'='PRETEND'
(Other definitions for pretend that I've seen before include "Dissemble" , "Profess falsely" , "Simulated" , "Behave unnaturally" , "Suppose" .)