Perfect sun welcomed by a Scottish isle (8)
I believe the answer is:
absolute
'perfect' is the definition.
(synonyms)
'sun welcomed by a scottish isle' is the wordplay.
'sun' becomes 'sol' (Latin for 'sun').
'welcomed by' means one lot of letters goes inside another (letters welcomed inside).
'scottish isle' becomes 'bute' (I've seen this before).
'a'+'bute'='abute'
'sol' put within 'abute' is 'ABSOLUTE'.
(Other definitions for absolute that I've seen before include "decided" , "Unconditional, downright," , "Not qualified; total" , "Complete - unlimited" , "sure" .)