Fools turning up in health resorts (4)
I believe the answer is:
spas
'health resorts' is the definition.
(I've seen this before)
'fools turning up' is the wordplay.
'fools' becomes 'saps' ('sap' can be a synonym of 'fool').
'turning up' is a reversal indicator.
'saps' reversed gives 'SPAS'.
'in' acts as a link.
(Other definitions for spas that I've seen before include "Health resorts near springs" , "Bath and suchlike" , "Mineral springs" .)