Rapid foxtrot by topless performers (4)
I believe the answer is:
fast
'rapid' is the definition.
(similar in meaning)
'foxtrot by topless performers' is the wordplay.
'foxtrot' becomes 'f' (phonetic alphabet: alpha, bravo, charlie etc.).
'by' says to put letters next to each other.
'topless' means to remove the first letter.
'performers' becomes 'cast' (I've seen this before).
'cast' with its first letter taken away is 'ast'.
'f'+'ast'='FAST'
(Other definitions for fast that I've seen before include "requiring only brief exposure" , "Eat nothing" , "requirement before surgery" , "Unlikely to run" , "Quick; firmly fixed" .)