Author is yellow, then in good health (6)
I believe the answer is:
orwell
'author' is the definition.
(I've seen this before)
'yellow then in good health' is the wordplay.
'yellow' becomes 'or' (heraldic term).
'then' is a charade indicator (letters next to each other).
'in good health' becomes 'well' ('well' can be similar in meaning to 'in good health').
'or'+'well'='ORWELL'
'is' acts as a link.
(Other definitions for orwell that I've seen before include "who wrote novels?" , "River" , "Author of 1984 etc" , "George --, novelist" , "George -, nineteen eighty-four author" .)