One highly strung in horrid pub, we may hear (6)
I believe the answer is:
violin
'horrid pub we may hear' is the definition.
I can't judge whether this definition defines the answer.
'one highly strung in' is the wordplay.
'one highly strung' becomes 'viol' (I am not sure about this - if you are sure you should believe this answer much more).
'viol'+'in'='VIOLIN'
Can you help me to learn more?
(Other definitions for violin that I've seen before include "It'a played with a bow" , "A stringed musical instrument, say a Stradivarius" , "Nigel Kennedy instrument" , "Bowed instrument" , "Menuhin's instrument" .)