Active nurses out dancing (9)
I believe the answer is:
strenuous
'active' is the definition.
(thesaurus)
'nurses out dancing' is the wordplay.
'dancing' indicates an anagram.
'nurses'+'out'='nursesout'
'nursesout' with letters rearranged gives 'STRENUOUS'.
(Other definitions for strenuous that I've seen before include "Requiring great effort" , "requiring much effort" , "Physically demanding" , "Vigorous" , "Needing much effort" .)