Container ship's beginning to be besieged by enemy fire (5)
I believe the answer is:
flask
'container' is the definition.
(flask is a kind of container)
'ship's beginning to be besieged by enemy fire' is the wordplay.
'beginning to' says to take the initial letters.
'be besieged by' means one lot of letters goes inside another (I've seen this in other clues).
'enemy fire' becomes 'flak' (flak is a kind of fire. I am not sure about the 'enemy' bit.**).
The initial letter of 'ships' is 's'.
's' inserted inside 'flak' is 'FLASK'.
Can you help me to learn more?
(Other definitions for flask that I've seen before include "Glass container" , "Container for liquids" , "Small pocket bottle" , "Portable drink container" .)