Move furtively around aristocrat, upset (5)
I believe the answer is:
creep
'move furtively' is the definition.
(I've seen this in another clue)
'around aristocrat upset' is the wordplay.
'around' becomes 'c' (abbreviation for 'circa').
'aristocrat' becomes 'peer' (peer is a kind of aristocrat).
'upset' shows that the letters should be reversed in order.
'peer' back-to-front is 'reep'.
'c'+'reep'='CREEP'
(Other definitions for creep that I've seen before include "Steal" , "wretch" , "Fawn" , "Tiptoe" , "Move slowly and stealthily" .)