Old woman, behold, in a sense peculiar (9)
I believe the answer is:
anomalous
'peculiar' is the definition.
(I've seen this before)
'old woman behold in a sense' is the wordplay.
'old woman' becomes 'ma' (I've seen this in other clues).
'behold' becomes 'lo'.
'in' indicates putting letters inside.
'sense' becomes 'nous' (nous is a kind of sense**).
'ma'+'lo'='malo'
'a'+'nous'='anous'
'malo' going within 'anous' is 'ANOMALOUS'.
(Other definitions for anomalous that I've seen before include "Peculiar" , "Inconsistent, deviating from the norm" , "Abnormal, deviant" , "Non-standard" , "Atypical, exceptional" .)