Army threat to Navy? (7)
I believe the answer is:
octopus
'army threat' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'to navy?' is the wordplay.
I cannot quite understand how this works, but
'to' is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for octopus that I've seen before include "Cephalopod with suckered tentacles" , "Sea-creature" , "Cop-outs (anag.)" , "Cops out (anag.)" , "Tentacled marine mollusc" .)