Good Scottish party welcomed by eg assistance animal (5,3)
I believe the answer is:
guide dog
'assistance animal' is the definition.
(I know that guide dog is a type of service dog)
'good scottish party welcomed by eg' is the wordplay.
'good scottish' becomes 'guid' (Scottish version of 'good').
'party' becomes 'do' (do is a kind of party).
'welcomed by' means one lot of letters goes inside another (letters welcomed inside).
'do' inserted inside 'eg' is 'edog'.
'guid'+'edog'='GUIDE-DOG'
(Other definitions for guide dog that I've seen before include "Blind person's helper" , "Blind person's aid" , "Aid for blind person" , "Aid for the visually impaired" , "blind leader" .)