Economise, writing novel in health resort, mostly (5)
I believe the answer is:
skimp
'economise' is the definition.
(as in skimping and saving)
'novel in health resort mostly' is the wordplay.
'novel' becomes 'kim' (Rudyard Kipling novel).
'in' is an insertion indicator.
'health resort' becomes 'spa' (spa can mean a health resort).
'mostly' means to remove the last letter.
'spa' with its last letter removed is 'sp'.
'kim' going within 'sp' is 'SKIMP'.
'writing' acts as a link.
(Other definitions for skimp that I've seen before include "Limit in quality or quantity" , "tighten one's belt" , "Be mean with, scamp" , "Be mean towards" , "Use minimal amount" .)