Natural to accept cook, oddly, must be rambling (10)
I believe the answer is:
incoherent
'rambling' is the definition.
(similar in meaning)
'natural to accept cook oddly' is the wordplay.
'natural' becomes 'inherent' (I've seen this before).
'to accept' means one lot of letters goes inside another.
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
The alternate letters of 'cook' are 'co'.
'inherent' going around 'co' is 'INCOHERENT'.
'must be' acts as a link.
(Other definitions for incoherent that I've seen before include "rambling" , "drunk?" , "Unintelligible" , "difficult to understand" , "Confused" .)