Clown’s elevation still lacking, last time (5)
I believe the answer is:
'clown's elevation' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'still lacking last time' is the wordplay.
'lacking' means to remove the last letter (the word is incomplete or lacking).
'last time' becomes 't' (abbreviation. I am not sure about the 'last' bit.).
'still' with its final letter taken away is 'stil'.
Can you help me to learn more?
(Other definitions for stilt that I've seen before include "Supporting column driven into the ground - wading bird" , "Wading bird; post" , "Walking pole; wader" , "Long-legged bird" , "laboured and unnatural in the past" .)