Scrawnier, oddly deficient stick (4)
I believe the answer is:
cane
'stick' is the definition.
(I know that cane is a type of stick)
'scrawnier oddly deficient' is the wordplay.
'oddly deficient' means one should take alternating letters (letters in odd-numbered positions removed).
The alternate letters of 'scrawnier' are 'CANE'.
(Other definitions for cane that I've seen before include "Slender stem of bamboo etc" , "Sugar plant" , "Eg, rattan" , "Walking stick; punish" , "Punish; woody stem" .)