Lobby people to accept unlimited lucid dream (13)
I believe the answer is:
hallucination
'dream' is the definition.
(thesaurus)
'lobby people to accept unlimited lucid' is the wordplay.
'lobby' becomes 'hall' (synonyms).
'people' becomes 'nation' ().
'to accept' means one lot of letters goes inside another.
'unlimited' means to look at the middle letters (discard the edges or 'limits' of the word).
The middle of 'lucid' is 'uci'.
'hall'+'nation'='hallnation'
'hallnation' placed around 'uci' is 'HALLUCINATION'.
(Other definitions for hallucination that I've seen before include "Alleged perception of non-existent things" , "Illusory perception" , "Trip" , "Mental aberration" , "Illusion" .)