Turned on about revised rate? Don't be so naive (3,4)
I believe the answer is:
get real
'don't be so naive' is the definition.
(phrase used to tell someone to be more realistic)
'turned on about revised rate?' is the wordplay.
'turned on' becomes 'gel' (I can't explain this - if you can you should give a lot more credence to this answer).
'about' is an insertion indicator.
'revised' is an anagram indicator.
'rate' with letters rearranged gives 'trea'.
'gel' going around 'trea' is 'GET REAL'.
Can you help me to learn more?
(Other definitions for get real that I've seen before include "Wake up and smell the coffee" , "Don't kid yourself!" , "(but don't buy instant)" .)