Beg doggedly not to go to bed (3,2)
I believe the answer is:
sit up
'to bed' is the definition.
Although both the answer and definition are verbs in their base form, I don't understand how one could define the other.
'beg doggedly not to go' is the wordplay.
I cannot really understand how this works, but
'go' could be 'sit' (sitting is a kind of going) and 'sit' is found within the answer.
The remaining letters 'up' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sit up that I've seen before include "Means to deal with corporation, maybe" , "Don't slouch" , "Stay downstairs late" , "form of exercise" , "Postpone bedtime" .)