Nuclear head a Terran left out ... almost a disaster (4,5)
I believe the answer is:
near thing
'almost a disaster' is the definition.
(I've seen this before)
'nuclear head a terran left' is the wordplay.
I cannot quite see how this works, but
'nuclear' could be 'n' (abbreviation) and 'n' is present in the answer.
'head' could be 'ear' (I have seen 'Head of corn' mean 'ear' so perhaps 'head' could also mean 'ear') and 'ear' is located in the answer.
The remaining letters 'thing' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'out' is the link.
Can you help me to learn more?
(Other definitions for near thing that I've seen before include "Narrow escape, missed by a small margin (4.5)" , "Knife-edge event" , "almost a disaster" , "Something that barely avoids failure or disaster" , "Close call" .)