Bert's partner (5)
I believe the answer is:
ernie
'bert's partner' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ernie that I've seen before include "Machine that randomly selects Premium Bond winners" , "Premium Bonds selection computer" , "- (the Fastest Milkman in the West) (Benny Hill)" , "Wise for instance" , "- - Bevin, 13 dn" .)