Oh please, get down from there! (4,3,2)
I believe the answer is:
come off it
'get down from there' is the definition.
(I've seen this before)
'oh please' is the wordplay.
I cannot quite see how this works, but
'oh' could be 'o' and 'o' is found in the answer.
'please' could be 'o' (form of address eg in an ode) and 'o' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for come off it that I've seen before include "that's most unlikely" , "Drug addict should" , "Don't talk rubbish" , "You're mad!" , "stop behaving like that!" .)