Showed old Scot in action (8)
I believe the answer is:
depicted
'showed' is the definition.
('depict' can be a synonym of 'show')
'old scot in action' is the wordplay.
'old scot' becomes 'Pict' (ancient people in Scotland during Roman times).
'in' means one lot of letters goes inside another.
'action' becomes 'deed' (deed is a kind of action).
'pict' placed within 'deed' is 'DEPICTED'.
(Other definitions for depicted that I've seen before include "Described or portrayed in words" , "Shown" .)