Second secretary in health resort (3)
I believe the answer is:
spa
'health resort' is the definition.
(spa can mean a health resort)
'second secretary' is the wordplay.
'second' becomes 's' (common abbreviation).
'secretary' becomes 'PA' (abbreviation for personal assistant).
's'+'pa'='SPA'
'in' acts as a link.
(Other definitions for spa that I've seen before include "Mineral-water resort" , "E.g. Harrogate" , "Health resort near a spring" , "Where people go for spring" , "Health and beauty treatment establishment" .)