Name second thief? (8)
I believe the answer is:
monicker
'name' is the definition.
'second thief?' is the wordplay.
'second' becomes 'mo' (both are short periods of time).
'thief?' becomes 'nicker' (someone who nicks or steals things).
'mo'+'nicker'='MONICKER'
(Other definitions for monicker that I've seen before include "Handle" , "Name (sl)" , "Nickname (slang)" , "Name or nickname" .)