The most common and most likely answer to this crossword clue is the 5 letter word SCOLD
I've seen this crossword clue in The Guardian
S
C
O
L
D
More clues leading to the result SCOLD
- Carpet that is past its best
- Carpet that is ancient, small and austere
- Nag disposed of, about a hundred
- Angrily rebuke son lacking warmth
- Reprimand Surrey captain over loftily dropping openers
- Rate little son ‘unemotional’
- Small unfeeling quarrelsome woman of old?
- South getting icy blast
- Dress down, feeling the chill after the end of mass
- Son gets unfriendly reprimand
Buddy explains!

The straight part
We know that "Nag" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nag = scold.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SCOLD mean?
SCOLD verb- To burn with hot liquid.
- To heat almost to boiling.
- A person who habitually scolds, in particular a troublesome and angry woman.
- To rebuke angrily.