Age-old ice show's slammed as a pointless exercise (4-5,5)
I believe the answer is:
wild-goose chase
'a pointless exercise' is the definition.
'age-old ice show's slammed' is the wordplay.
'slammed' indicates anagramming the letters.
'age'+'old'+'ice'+'shows'='ageoldiceshows'
'ageoldiceshows' is an anagram of 'WILD-GOOSE CHASE'.
'as' is the link.
(Other definitions for wild-goose chase that I've seen before include "Hopeless quest" , "A foolish pursuit" , "Futile quest" .)