Dim as could be, the king had ass’s ears (5)
I believe the answer is:
midas
'the king had ass's ears' is the definition.
I can't tell whether this defines the answer.
'dim as could be' is the wordplay.
'could be' indicates an anagram.
'dim'+'as'='dimas'
'dimas' is an anagram of 'MIDAS'.
Can you help me to learn more?
(Other definitions for midas that I've seen before include "Everything he touched turned to gold" , "Phrygian king" , "Gold-creating king" , "my gift turned out a curse" , "One with a golden touch" .)