Copy produced by the environmentalists doing a U-turn (3)
I believe the answer is:
Here is my best explanation:
'copy' is the definition.
('ape' can be a synonym of 'copy')
'by the environmentalists doing a u-turn' is the wordplay.
'by' is a charade indicator (letters next to each other).
'the environmentalists doing' becomes 'ep' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'u-turn' is a reversal indicator.
'ep' next to 'a' is 'epa'.
'epa' reversed gives 'APE'.
'produced' acts as a link.
(Other definitions for ape that I've seen before include "Simian - copy", "Mimic the primate", "Imitate, clumsy person (colloq.)", "Anthropoid primate", "Take off", "Clumsy person", "Imitate like primate", "Large primate", "Creature" and "Monkey".)