Promoters of health resort show influencers here (4,3)
I believe the answer is:
whos who
'influencers here' is the definition.
(book listing influential people)
'promoters of health resort show' is the wordplay.
'promoters of health' becomes 'WHO' (World Health Organisation).
'resort' indicates an anagram.
'show' anagrammed gives 'swho'.
'who'+'swho'='WHOS WHO'
(Other definitions for whos who that I've seen before include "Directory of people" , "Book listing notable people (3'1,3)" , "Directory of notables" , "Celebrities' reference book" , "Lexicon or VIPs" .)