Bitter Englishman discontented tranquil hosts (9)
I believe the answer is:
resentful
'bitter' is the definition.
(synonyms)
'englishman discontented tranquil hosts' is the wordplay.
'discontented' suggests removing the centre (the word's contents are removed).
'tranquil' becomes 'restful' (I've seen this in another clue).
'hosts' is an insertion indicator (inserted letters are welcomed or hosted).
'englishman' with its centre removed is 'en'.
'en' going within 'restful' is 'RESENTFUL'.
(Other definitions for resentful that I've seen before include "Feeling indignation" , "Bearing a grudge" , "Embittered - nurse left (anag)" , "Grudging" , "Bitter" .)