It's an idea to turn up healthy to the doctor (5)
I believe the answer is:
motif
'it's an idea' is the definition.
(motif is a kind of idea)
'turn up healthy to the doctor' is the wordplay.
'turn up' says the letters should be written backwards.
'healthy' becomes 'fit' (associated in meaning).
'to' says to put letters next to each other (I've seen this in other clues).
'the doctor' becomes 'mo' (medical officer).
'fit' in reverse letter order is 'tif'.
'tif' after 'mo' is 'MOTIF'.
'to' is the link.
(Other definitions for motif that I've seen before include "Recurring image in design" , "Theme, perhaps musical" , "Characteristic theme" , "Theme or recurring feature in music or writing" , "Theme in a work of art" .)