Environmentalist coming to land gets signal to go (5,5)
I believe the answer is:
green light
'to go' is the definition.
(I've seen this before)
'environmentalist coming to land' is the wordplay.
'environmentalist' becomes 'green' (member of the Green Party).
'coming to' says to put letters next to each other.
'land' becomes 'light' (light can mean to settle or land).
'green'+'light'='GREEN LIGHT'
'gets signal' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for green light that I've seen before include "Seal of approval" , "Sanction" , "Signal of consent" , "Signal to proceed" , "OK" .)