She's the one (4)
'she's' is the definition.
'the one' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'the'+'a'='THEA'
(Other definitions for thea that I've seen before include "Female name meaning 'goddess'" , "Girl's name, tea genus" , "Plant" , "evergreen shrubs?" , "... Girl" .)
'she's' is the definition.
'one' is the wordplay.
I cannot really understand how this works, but
'one' could be 'un' (northern English dialect form of 'one') and 'un' is located in the answer.
A single letter 'a' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'the' is the link.
Can you help me to learn more?
(Other definitions for una that I've seen before include "She's one in Italy." , "Diego's one" , "- - Stubbs, comedy actress" , "of satellite with no sides" , "Girl" .)