Musician with history including activity during the Blitz (7)
I believe the answer is:
harpist
'musician' is the definition.
(harpist is a kind of musician)
'history including activity during the blitz' is the wordplay.
'history' becomes 'hist' (academic abbreviation).
'including' indicates putting letters inside.
'activity during the blitz' becomes 'arp' (abbreviation for Air Raid Precautions).
'hist' going around 'arp' is 'HARPIST'.
'with' is the link.
(Other definitions for harpist that I've seen before include "Stringed instrument player" , "Instrumentalist" , "musician" .)