Dog in New Jersey, one attached to army HQ (7)
I believe the answer is:
basenji
'dog' is the definition.
(I know that basenji is a type of dog)
'new jersey one attached to army hq' is the wordplay.
'new jersey' becomes 'nj' (abbreviation).
'one' becomes 'i' (Roman numeral).
'attached to' says to put letters next to each other.
'army hq' becomes 'base' (I can't justify this - if you can you should give a lot more credence to this answer).
'nj'+'i'='nji'
'nji' put after 'base' is 'BASENJI'.
'in' is the link.
Can you help me to learn more?
(Other definitions for basenji that I've seen before include "Smallish hunting dog" , "Dog unable to bark" , "Barkless dog" , "Breed of African hunting dog that rarely barks" , "Small hunting dog" .)