Horrid friend by end of meal mocking hosts (9)
I believe the answer is:
appalling
'horrid' is the definition.
(thesaurus)
'friend by end of meal mocking hosts' is the wordplay.
'friend' becomes 'pal' (pal is a kind of friend).
'by' is a charade indicator (letters next to each other).
'end of' suggests the final letters.
'mocking' becomes 'aping' (aping is a kind of mocking).
'hosts' indicates putting letters inside.
The last letter of 'meal' is 'l'.
'pal'+'l'='pall'
'pall' placed inside 'aping' is 'APPALLING'.
(Other definitions for appalling that I've seen before include "page entirely covered in copying" , "Terrible" , "Dreadful" , "Shocking, outrageous" , "Shockingly bad" .)