Bottle finally explodes in intense fire (5)
I believe the answer is:
flask
'bottle' is the definition.
(I know that flask is a type of bottle)
'finally explodes in intense fire' is the wordplay.
'finally' says to take the final letters.
'in' means one lot of letters goes inside another.
'intense fire' becomes 'flak' (synonyms. I am not sure about the 'intense' bit.).
The final letter of 'explodes' is 's'.
's' going inside 'flak' is 'FLASK'.
Can you help me to learn more?
(Other definitions for flask that I've seen before include "Portable drink container" , "Small pocket bottle" , "Glass container" , "Container for liquids" .)