Give something back, go on (5)
I believe the answer is:
grant
'give' is the definition.
(to grant someone something is to give them it)
'something back go on' is the wordplay.
'back' says to take the final letters (the letter at the back).
'go' becomes 'rant' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' says to put letters next to each other.
The last letter of 'something' is 'g'.
'g'+'rant'='GRANT'
Can you help me to learn more?
(Other definitions for grant that I've seen before include "Agree to - bursary" , "former president" , "Monetary aid" , "... Cambridgeshire village" , "Concede, like an American general" .)