Health club class (4)
I believe the answer is:
yoga
'health club class' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for yoga that I've seen before include "E.g. Lotus position" , "Hindu spiritual and ascetic discipline" , "Hindu philosophical system" , "Hindu system for health and relaxation" , "Spiritual exercise discipline" .)