Tightrope walker goes around one of the levels (4)
I believe the answer is:
tier
'one of the levels' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'tightrope walker goes around' is the wordplay.
'tightrope walker' becomes 'tie' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'goes' becomes 'purrs' (purring is a kind of going).
'around' says to take the centre.
The centre of 'purrs' is 'r'.
'tie'+'r'='TIER'
Can you help me to learn more?
(Other definitions for tier that I've seen before include "Row in theatre" , "Storey" , "One who secures" , "Bank - row" , "Rank - row" .)