Understood after holding one's own tool (6,3)
I believe the answer is:
coping saw
'tool' is the definition.
(coping saw is a kind of tool)
'understood after holding one's own' is the wordplay.
'understood' becomes 'saw' ('see' can be a synonym of 'understand').
'after' says to put letters next to each other.
'holding one's own' becomes 'coping'.
'saw' put after 'coping' is 'COPING-SAW'.
(Other definitions for coping saw that I've seen before include "Tool" , "help in cutting corners?" , "cutter" .)