Person with fancy ideas (7)
I believe the answer is:
dreamer
'person' is the definition.
(dreamer is a kind of person)
'fancy ideas' is the wordplay.
'fancy' becomes 'dream' (I've seen this before).
'ideas' becomes 'er' (I am not sure about this - if you are sure you should believe this answer much more).
'dream'+'er'='DREAMER'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for dreamer that I've seen before include "He has visions" , "Idealist - visionary" , "Gerontius" , "stargazer" , "One imagines" .)