Atomic Navy gets upset about cryptic clue (7)
I believe the answer is:
nuclear
'atomic' is the definition.
(I know that atomic can be written as nuclear)
'navy gets upset about cryptic clue' is the wordplay.
'navy' becomes 'ran' (I can't justify this - if you can you should believe this answer much more).
'gets upset' is a reversal indicator (I've seen 'getting upset' mean this).
'about' is an insertion indicator.
'cryptic' indicates anagramming the letters (a cryptic or obscure order of the letters).
'ran' backwards is 'nar'.
'clue' is an anagram of 'ucle'.
'nar' enclosing 'ucle' is 'NUCLEAR'.
Can you help me to learn more?
(Other definitions for nuclear that I've seen before include "Relating to atomic weapons" , "Type of reaction" , "Using fission or fusion" , "Concerning subatomic particles" , "winter, sort of" .)