You say leading Scotsman's ideal (7)
I believe the answer is:
utopian
'ideal' is the definition.
('utopian' can be similar in meaning to 'ideal')
'you say leading scotsman's' is the wordplay.
'you' becomes 'u' (I've seen this in other clues).
'say' becomes 'top'.
'leading' is a charade indicator (letters next to each other).
'scotsman' becomes 'ian'.
'u'+'top'+'ian'='UTOPIAN'
(Other definitions for utopian that I've seen before include "Citizens of Thomas More's perfect country" , "ideal but unrealistic" , "Of Thomas More's perfect place" , "Of supposed perfection" , "Idealistic but usually impractical" .)