Health in Spring primarily needs extra strong sunshine (8)
I believe the answer is:
wellness
'health' is the definition.
(I've seen this before)
'spring primarily needs extra strong sunshine' is the wordplay.
'spring' becomes 'well' (both can mean a source of water).
'primarily' indicates taking the first letters.
The initial letters of 'needs extra strong sunshine' is 'ness'.
'well'+'ness'='WELLNESS'
'in' acts as a link.
(Other definitions for wellness that I've seen before include "Health" , "good condition" .)