Had a picnic? (3,3)
I believe the answer is:
ate out
'had a picnic?' is the definition.
The answer and definition can be both related to consumption as well as being past participle verbs.
Perhaps they are linked in a way I don't understand?
'had a picnic?' is the wordplay.
'had' becomes 'ate' (e.g. I had an ice cream).
'a picnic?' becomes 'out' (I can't explain this - if you can you should believe this answer much more).
'ate'+'out'='ATE OUT'
Can you help me to learn more?
(Other definitions for ate out that I've seen before include "'Didn't dine at home (3,3)'" , "Had dinner in restaurant" , "didn't cook at home?" .)