Navy uniform in stock provides chest brace (7)
I believe the answer is:
sternum
'chest brace' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'navy uniform in stock' is the wordplay.
'navy' becomes 'RN' (abbreviation for Royal Navy).
'uniform' becomes 'U' (phonetic alphabet: alpha, bravo, charlie etc.).
'in' indicates putting letters inside.
'stock' becomes 'stem' (I can't justify this - if you can you should give a lot more credence to this answer).
'rn'+'u'='rnu'
'rnu' placed inside 'stem' is 'STERNUM'.
'provides' is the link.
Can you help me to learn more?
(Other definitions for sternum that I've seen before include "big bone" , "Munster (anag.)" , "somewhere in chest" , "front of breast" , "Breastbone" .)