Start on, but find oneself bogged down by? (3,5,2)
I believe the answer is:
get stuck in
'start on' is the definition.
Both the answer and definition are verbs in their base form.
Perhaps you can see a link between them that I can't see?
'find oneself bogged down by?' is the wordplay.
I cannot quite see how this works, but
'find' could be 'get' ('get' can be a synonym of 'find') and 'get' is found in the answer.
This explanation may well be incorrect...
'but' acts as a link.
Can you help me to learn more?
(Another definition for get stuck in that I've seen is " Concentrate on your work!".)