It's something to go on (5,5)
I believe the answer is:
green light
'it's something to go on' is the definition.
(I've seen this before)
'it's something to go' is the wordplay.
I cannot really understand how this works, but
'to go' could be 're' (I've seen this in other clues) and 're' is found in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for green light that I've seen before include "Signal for go" , "Sanction" , "Seal of approval" , "What one has to go on" , "Signal of consent" .)