Bert's Muppet pal (5)
I believe the answer is:
ernie
'bert's muppet pal' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ernie that I've seen before include "Bondsman" , "Eric's other half" , "Guy" , "Els, for example" , "Selector of winning premium bond numbers" .)