Dance: fifty entertained by it, repeatedly (5)
I believe the answer is:
salsa
'dance' is the definition.
(type of dance)
'fifty entertained by it repeatedly' is the wordplay.
'fifty' becomes 'L' (Roman numeral).
'entertained by' means one lot of letters goes inside another (inserted letters are hosted or entertained).
'it' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'repeatedly' shows that letters should be duplicated.
'sa' doubled is 'sasa'.
'l' placed inside 'sasa' is 'SALSA'.
(Other definitions for salsa that I've seen before include "dressing" , "Latin-American dance" , "Spicy tomato sauce" , "Cuban dance music or spicy sauce" , "Spicy 7" .)