Sing about one tin (6)
I believe the answer is:
intone
'sing' is the definition.
(I know that intone has the is a more specific form of the action sing)
'about one tin' is the wordplay.
'about' indicates anagramming the letters.
'one'+'tin'='onetin'
'onetin' is an anagram of 'INTONE'.
(Other definitions for intone that I've seen before include "Recite in a chanting voice" , "Speak in chant or drone" , "Recite without inflection" , "Recite with little variation in pitch" , "Speak in chanting voice" .)