Help here, off and on, to provide sword (4)
I believe the answer is:
epee
'sword' is the definition.
(sword used in fencing)
'help here off and on' is the wordplay.
'off and on' indicates alternate letters (letters used at regular intervals).
'help'+'here'='helphere'
The alternating letters of 'helphere' are 'EPEE'.
'to provide' acts as a link.
(Other definitions for epee that I've seen before include "Type of sword" , "Use it to fence" , "Bit of fencing" , "Sharp-pointed duelling sword" , "Narrow fencing sword" .)