The Clue
Postscripts: Abbr. (3 letter answer)
The Answer
PSS
Tags
Notes
The answer PSS is common and appears about once every 275 puzzles.
Related Clues
Additions to ltrs.
Afterthoughts: Abbr.
Letter addenda
Letter afterthoughts
Ltr. addenda
Ltr. additions
Ltr. afterthoughts
Quick addenda
Supp. writings
Add-ons: Abbr.
Brief letter additions
Certain addenda: Abbr.
Ends of letters, briefly
Epistolary afterthoughts: Abbr.
Followers of closings: Abbr.
Letter addenda: Abbr.
Letter addenda, for short
Letter endings: Abbr.
Letter writer's afterthoughts
Letters after letters
Signature followers, for short
Some addenda, for short
Some afterthoughts, in brief
Some scribbles, for short
Supplementary words in a letter
They follow signatures
Endings to some e-mails
Endings to some letters, for short
Remarks akin to "btw"
Letter add-ons: Abbr.
Letter add-ons, for short
Notes added to notes: Abbr.
They go below signatures, briefly
They go below signatures, for short
They're not part of the body: Abbr.