Lived in swashbuckling times (3)
I believe the answer is:
was
'lived' is the definition.
('be' can be a synonym of 'live')
'in swashbuckling times' is the wordplay.
'in' indicates a hidden word.
'WAS' can be found hidden inside 'swashbuckling times'.
(Other definitions for was that I've seen before include "Did live" , "Used to be" , "'Is, in the past (3)'" , "(He/she/it) existed" , "(He/she) existed" .)