Mostly indisposed, appear rejected? (9)
I believe the answer is:
unwelcome
'rejected?' is the definition.
(thesaurus)
'mostly indisposed appear' is the wordplay.
'mostly' means to remove the last letter.
'indisposed' becomes 'unwell' (synonyms).
'appear' becomes 'come' (come can mean to appear or arrive).
'unwell' with its last letter taken off is 'unwel'.
'unwel'+'come'='UNWELCOME'
(Other definitions for unwelcome that I've seen before include "Bad (news); not acceptable" , "Causing displeasure" , "displeasing!" , "No received with pleasure - by host?" , "Not greeted or received with pleasure, quite the opposite" .)