Stories of a bit of gallantry in the SAS (5)
I believe the answer is:
sagas
'stories' is the definition.
(saga is a kind of story)
'a bit of gallantry in the sas' is the wordplay.
'bit of' suggests taking the first letters.
'in' is an insertion indicator.
The first letter of 'gallantry' is 'g'.
'a'+'g'='ag'
'ag' put into 'sas' is 'SAGAS'.
'of' is the link.
(Other definitions for sagas that I've seen before include "Myths" , "Heroic tales" , "Tales of heroes" , "Long involved stories" .)