In the navy, a sound crew with faultless service (7)
I believe the answer is:
cruiser
'in the navy a' is the definition.
I can't judge whether this defines the answer.
'sound crew with faultless service' is the wordplay.
'sound' indicates a 'sounds like' (homophone) clue.
'with faultless service' becomes 'iser' (I can't justify this - if you can you should give a lot more credence to this answer).
'crew' is a homophone of 'cru'.
'cru'+'iser'='CRUISER'
Can you help me to learn more?
(Other definitions for cruiser that I've seen before include "Relatively fast warship" , "Pleasure craft" , "Old warship" , "Warship; leisure craft" , "Ship" .)