Senior turning in makes public U-turns (9)

'turns' is the definition.
(reversal is a kind of turn)

'senior turning in makes public' is the wordplay.
'senior' becomes 'sr' (abbreviation).
'turning' says the letters should be written backwards.
'in' indicates putting letters inside.
'makes public' becomes 'reveals' (I can't explain this - if you can you should believe this answer much more).
'sr' backwards is 'rs'.
'rs' put within 'reveals' is 'REVERSALS'.

'u' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.

Can you help me to learn more?