Start to launch missile right away in case (6)
I believe the answer is:
locket
'case' is the definition.
(locket is a kind of case)
'start to launch missile right away' is the wordplay.
'start' becomes 'lock' (I can't justify this - if you can you should believe this answer much more).
'launch' indicates taking the first letters (the letter which launches the word).
'right' suggests the final letters (the letter on the right of the word).
'away' indicates an anagram (letters move away from their original places).
The initial letter of 'to' is 't'.
The final letter of 'missile' is 'e'.
't'+'e'='te'
'te' is an anagram of 'et'.
'lock'+'et'='LOCKET'
'in' is the link.
Can you help me to learn more?
(Other definitions for locket that I've seen before include "Small ornamental case worn on a chain" , "Neck adornment" , "One round neck holding picture" , "'Small piece of jewellery, it opens (6)'" , "Small ornamental case around the neck" .)