Cranefly grub (13)
I believe the answer is:
leatherjacket
'cranefly grub' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for leatherjacket that I've seen before include "Swimmer" , "Cranefly larva" , "Cranefly grub" , "Garden pest - crane fly larva" , "Hold close" .)