Often drilling with part of plant (7)
I believe the answer is:
tendril
'part of plant' is the definition.
(I've seen this before)
'often drilling with' is the wordplay.
'with' indicates the answer is hidden within the clue.
'TENDRIL' can be found hidden inside 'often drilling'.
(Other definitions for tendril that I've seen before include "Part of twining plant" , "Natural thread climbing plants produce to attach to a support" , "Coiling shoot of climbing plant" , "Climbing plant's gripper" , "Climbing plant's grasper" .)