Noted skill of chap on vessel inspiring American firm once (12)
I believe the answer is:
musicianship
'noted skill' is the definition.
(as in musical notes)
'chap on vessel inspiring american firm once' is the wordplay.
'chap' becomes 'man' (chap can mean a man).
'on vessel' becomes 'ship' (I can't explain this - if you can you should believe this answer much more).
'inspiring' indicates putting letters inside.
'american' becomes 'us' (abbreviation for United States).
'firm once' becomes 'ICI' (Imperial Chemical Industries, former company).
'man'+'ship'='manship'
'us'+'ici'='usici'
'manship' placed around 'usici' is 'MUSICIANSHIP'.
'of' acts as a link.
(Other definitions for musicianship that I've seen before include "Note skill" , "Player's skill" , "ability to play" , "Instrumental prowess - Pisa is Munich (anag)" .)