Immature university lover depended on changing (14)
I believe the answer is:
underdeveloped
'immature' is the definition.
(thesaurus)
'university lover depended on changing' is the wordplay.
'university' becomes 'u' (abbreviation for university).
'on' means one lot of letters go next to another.
'changing' indicates an anagram.
'lover' after 'depended' is 'dependedlover'.
'dependedlover' is an anagram of 'nderdeveloped'.
'u'+'nderdeveloped'='UNDERDEVELOPED'
(Other definitions for underdeveloped that I've seen before include "(Of a country) not economically advanced" , "(Of a country/region) not economically advanced" .)