Scottish scam taking in Welshman — and Scot, perhaps (10)

'scottish' is the definition.
(Caledonian means relating to Scotland)

'scam taking in welshman and scot perhaps' is the wordplay.
'scam' becomes 'con' (both can mean a fraudulent scheme).
'taking in' is an insertion indicator.
'welshman' becomes 'aled' (I've seen this in other clues).
'and' means one lot of letters go next to another.
'scot perhaps' becomes 'Ian' (Ian is a common Scottish name).
'con' going around 'aled' is 'caledon'.
'caledon'+'ian'='CALEDONIAN'