Activate the gum, perhaps (7)
I believe the answer is:
moisten
'activate' is the definition.
The answer and definition can be both related to change as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for moisten that I've seen before include "Make damp, say lips with tongue" , "contrary to sixteen down [DEHYDRATE]!" , "water a bit" , "What one's eyes may do!" , "It's on me (anag)" .)