Drill ending in coolant, wet (8)
I believe the answer is:
training
'drill' is the definition.
(I've seen this before)
'ending in coolant wet' is the wordplay.
'ending' becomes 'train' (train is a kind of ending).
'in coolant wet' becomes 'ing' (I can't explain this - if you can you should give a lot more credence to this answer).
'train'+'ing'='TRAINING'
Can you help me to learn more?
(Other definitions for training that I've seen before include "Exercising" , "drill" , "Instructing, teaching" , "Prepare for a competition or career" , "Tuition" .)