A health resort some patients attend initially (3)
I believe the answer is:
spa
'a health resort' is the definition.
(spa can mean a health resort)
'some patients attend initially' is the wordplay.
'initially' indicates taking the first letters.
The first letters of 'some patients attend' is 'SPA'.
(Other definitions for spa that I've seen before include "Mineral-water resort" , "Watering hole" , "A curative mineral spring, or place with one" , "Water source" , "Watering-place" .)