Stir fast? (6,6)
I believe the answer is:
hunger strike
'fast?' is the definition.
(hunger strike is a kind of fast)
'stir' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'stir' is 'stri' which is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for hunger strike that I've seen before include "Starvation protest" , "Non-violent protest" , "fast" .)