Athenian way of working in tin (5)
I believe the answer is:
timon
'athenian' is the definition.
(as in Shakespeare's Timon of Athens)
'way of working in tin' is the wordplay.
'way of working' becomes 'mo' (abbreviation for modus operandi).
'in' indicates putting letters inside.
'mo' going into 'tin' is 'TIMON'.
(Other definitions for timon that I've seen before include "Shakespearean Athenian" , "Athenian in Shakespeare play" , "- - of Athens (Shakespeare)" , "lead in Greek tragedy?" , "title role" .)