Adjusts clothing worn by Welsh person (9)
I believe the answer is:
redresses
'adjusts' is the definition.
Although both the answer and definition are verbs in their -s form, I can't see how they can define each other.
'clothing worn by welsh person' is the wordplay.
'clothing' becomes 'dress' (dress is a kind of clothing).
'worn by' means one lot of letters goes inside another (outside letters are worn by those on the inside).
'welsh person' becomes 'rees' (I can't explain this - if you can you should believe this answer much more).
'dress' going inside 'rees' is 'REDRESSES'.
Can you help me to learn more?
(Other definitions for redresses that I've seen before include "Sets right, makes amends" , "Pays for" .)