A latitude supported by tenor over another singer (4)
I believe the answer is:
alto
'singer' is the definition.
(type of singing voice)
'a latitude supported by tenor over another' is the wordplay.
'latitude' becomes 'L' (abbreviation for latitude).
'supported by' means one lot of letters go next to another (in a down clue, some letters hold up others).
'tenor' becomes 't'.
'over' is a charade indicator (letters next to each other) (in a down clue, some letters go over others).
'another' becomes 'o' (I've seen this in other clues).
'a'+'l'+'t'+'o'='ALTO'
(Other definitions for alto that I've seen before include "Unisex vocal range" , "A singing voice or pitch" , "Singer's hidden inside chemical toilet" , "The highest adult male singing-voice" , "Singing range" .)