Begin by shoving hard to stop cat biting (4-5)
I believe the answer is:
push-start
'begin' is the definition.
Both the answer and definition are verbs in their base form.
Maybe there's a link between them I don't understand?
'shoving hard to stop cat biting' is the wordplay.
I cannot quite see how this works, but
'hard' could be 'h' (abbreviation used in pencil classifications) and 'h' is found in the answer.
'cat' could be 'puss' (puss is a kind of cat) and 'puss' is found within the remaining letters.
'biting' could be 'tart' (both can mean acerbic) and 'tart' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'by' acts as a link.
Can you help me to learn more?
(Another definition for push-start that I've seen is " Get car going with shove".)