Knotty absence of medication? (6)
I believe the answer is:
nodose
'knotty' is the definition.
(I've seen this before)
'absence of medication?' is the wordplay.
'absence of' becomes 'no'.
'medication?' becomes 'dose' (dose is a kind of medication).
'no'+'dose'='NODOSE'
(Other definitions for nodose that I've seen before include "with knots" , "Lumpy and swollen" , "covered with swellings" , "Odeons (anag.); knotty" , "Having knot-like swellings" .)