Start, as thieves may, to engage with two breaking in (3-4)

I believe the answer is:

hot-wire

'start as thieves may' is the definition.
(how a thief might start a car)

'engage with two breaking in' is the wordplay.
'engage with' becomes 'hire' (engage can mean to hire someone's services. I am not sure about the 'with' bit.).
'breaking' indicates an anagram.
'in' is an insertion indicator.
'two' is an anagram of 'otw'.
'hire' placed around 'otw' is 'HOT-WIRE'.

'to' acts as a link.

(Another definition for hot-wire that I've seen is " Make unorthodox start".)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app