Up to the task? Even Ray Bolger! (4)
I believe the answer is:
able
'up to the task?' is the definition.
(I've seen this in another clue)
'even ray bolger' is the wordplay.
'even' means one should take alternating letters (even-numbered letters are used).
'ray'+'bolger'='raybolger'
The alternate letters of 'raybolger' are 'ABLE'.
(Other definitions for able that I've seen before include "Having the necessary capacity (to do something)" , "Having great proficiency or intelligence" , "Competent as seaman may be" , "Having considerable skill" , "Clever skilful" .)