Nick entertained by a short musical circus performer (7)
I believe the answer is:
acrobat
'circus performer' is the definition.
(type of performing gymnast)
'nick entertained by a short musical' is the wordplay.
'nick' becomes 'rob' (I've seen this in other clues).
'entertained by' indicates putting letters inside (I've seen this in other clues).
'short musical' becomes 'cat' (I am not sure about this - if you are sure you should believe this answer much more).
'a'+'cat'='acat'
'rob' going inside 'acat' is 'ACROBAT'.
Can you help me to learn more?
(Other definitions for acrobat that I've seen before include "Performer going head over heels?" , "Agile entertainer" , "Athletic Circus Performer" , "Rope-dancer" , "Athletic type" .)