Sort of lead mother will follow in principle (5)
I believe the answer is:
dogma
'principle' is the definition.
(I know that dogma is a type of principle)
'sort of lead mother will follow' is the wordplay.
'sort of lead' becomes 'dog' (I can't justify this - if you can you should believe this answer much more).
'mother' becomes 'ma' (Ma is another word for mother or mum).
'will follow' says to put letters next to each other.
'dog'+'ma'='DOGMA'
'in' is the link.
Can you help me to learn more?
(Other definitions for dogma that I've seen before include "Some believe it certainly" , "Inflexible principles" , "Opinion viewed as truth?" , "Item of belief" , "Inflexible doctrine" .)