Unpleasant people welcomed by nasty client (9)
I believe the answer is:
inclement
'unpleasant' is the definition.
('inclement' can be similar in meaning to 'unpleasant')
'people welcomed by nasty client' is the wordplay.
'people' becomes 'men' (man is a kind of person).
'welcomed by' indicates putting letters inside (I've seen this in other clues).
'nasty' is an anagram indicator.
'client' is an anagram of 'inclet'.
'men' going into 'inclet' is 'INCLEMENT'.
(Other definitions for inclement that I've seen before include "Rough" , "not fair" , "with heavens opening?" , "Weather so awful" , "severe" .)