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' indicates taking the first letters.
'in the' indicates putting letters inside.
The first letter of 'gallantry' is 'g'.
'a'+'g'='ag'
'ag' going into 'sas' is 'SAGAS'.
'of' acts as a link.
(Other definitions for sagas that I've seen before include "Myths" , "Heroic tales" , "Tales of heroes" , "Long involved stories" .)