Tight young lady narrowly avoided collision (4,4)
I believe the answer is:
near miss
'narrowly avoided collision' is the definition.
(near miss can mean a narrowly avoided crash)
'tight young lady' is the wordplay.
'tight' becomes 'near' (I've seen this in another clue).
'young lady' becomes 'miss' (term of address for a young woman).
'near'+'miss'='NEAR MISS'
(Other definitions for near miss that I've seen before include "Failure just" , "Falling close to but not on the target" , "reason for alarm or relief on aircraft?" , "Almost a hit" , "Narrowly-averted accident" .)