Plank defect (4)
I believe the answer is:
warp
'plank defect' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for warp that I've seen before include "Of wood, twist under heat" , "Distort as wood may from heat" , "Misintepret" , "Distort, ship's rope" , "Buckle" .)