Gave 'old-fashioned' to describe Old Norse (7)
I believe the answer is:
donated
'gave' is the definition.
(donating is a kind of giving)
'old-fashioned to describe old norse' is the wordplay.
'old fashioned' becomes 'dated' (I've seen this before).
'to describe' indicates putting letters inside.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'norse' becomes 'N' (abbreviation in linguistics).
'o'+'n'='on'
'dated' going around 'on' is 'DONATED'.
(Other definitions for donated that I've seen before include "Presented" , "Given" , "Gave" .)