Activists — people in tents drinking a gin excitedly (11)
I believe the answer is:
campaigners
'activists' is the definition.
(I've seen this before)
'people in tents drinking a gin excitedly' is the wordplay.
'people in tents' becomes 'campers' (I can't explain this - if you can you should believe this answer much more).
'drinking' means one lot of letters goes inside another (inserted letters are consumed or drunk).
'excitedly' indicates an anagram (letters excited or stimulated into a new form).
'a'+'gin'='agin'
'agin' is an anagram of 'aign'.
'campers' placed around 'aign' is 'CAMPAIGNERS'.
Can you help me to learn more?
(Another definition for campaigners that I've seen is " Activists".)