Devout woman has only to say the word (4)
I believe the answer is:
noun
'the word' is the definition.
(noun is a kind of word)
'devout woman has only' is the wordplay.
'devout woman' becomes 'nun' (I've seen this before).
'has' is an insertion indicator.
'only' becomes 'o' (this might be a standard abbreviation which I don't know about).
'nun' going around 'o' is 'NOUN'.
'to say' is the link.
Can you help me to learn more?
(Other definitions for noun that I've seen before include "Word identifying people, things, etc" , "Part of speech identifying a person, place or thing" , "Word that refers to a person, place or thing" , "Word referring to person, place or thing" , "Person, place, thing, state or quality?" .)