Became, when one left the road and steered towards (6,4)
I believe the answer is:
turned into
'became' is the definition.
('turn into' can be a synonym of 'become')
'one left the road and steered towards' is the wordplay.
I cannot really understand how this works, but
'one' could be 'o' (I've seen this in other clues) and 'o' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is found in the answer.
'left' could be 'red' (red can informally mean communist) and 'red' is found in the remaining letters.
This may be the basis of the clue (or it may be nonsense).
'when' is the link.
Can you help me to learn more?