Star keeping very cool when collecting a pat on the back (8)
I believe the answer is:
accolade
'star' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
I don't understand the remainder of the clue.
(Other definitions for accolade that I've seen before include "Praise publicly given" , "Praise or approval, accompanies awarding of knighthood" , "Praise or approval - or elevation to knighthood" , "Acclaim; mark of honour" , "Special honour as an acknowledgment of merit" .)