Social climber put off hosting celebrity (7)
I believe the answer is:
upstart
'social climber' is the definition.
(term for someone seeking higher social status)
'put off hosting celebrity' is the wordplay.
'off' indicates anagramming the letters.
'hosting' is an insertion indicator (inserted letters are welcomed in or hosted).
'celebrity' becomes 'star' (I've seen this before).
'put' is an anagram of 'upt'.
'upt' going around 'star' is 'UPSTART'.
(Other definitions for upstart that I've seen before include "Pipsqueak" , "Nouveau-riche" , "Arriviste, parvenu" , "Nouveau riche" , "Recent promotees, say, behaving with arrogance" .)