Saw lacking coolant? (7)
I believe the answer is:
noticed
'saw' is the definition.
(I've seen this before)
'lacking coolant?' is the wordplay.
I cannot really see how this works, but
'lacking' could be 'no' (I've seen this in other clues) and 'no' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for noticed that I've seen before include "regarded" , "Realised" , "Clocked" , "Spotted" , "Became aware of" .)