No change in gland (5)
I believe the answer is:
ovary
'gland' is the definition.
(I've seen this before)
'no change' is the wordplay.
'no' becomes 'o' (resembles 0 - 'no' can mean 'zero').
'change' becomes 'vary' ('vary' can be a synonym of 'change'**).
'o'+'vary'='OVARY'
'in' acts as a link.
(Other definitions for ovary that I've seen before include "Female reproductive gland" , "Egg-producing organ" , "Egg-producing gland" , "Fem. reproductive organ" , "Part of flower" .)