A play on words (3)
I believe the answer is:
pun
'a play on words' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for pun that I've seen before include "Humorous wordplay" , "Form of wordplay" , "Humorous play on words" , "A play on words, may be funny" , "A play on words - not the height of wit" .)