Gloomy number by clumsy Rob welcomed by Sue from the west (9)
I believe the answer is:
tenebrous
'gloomy' is the definition.
(I've seen this before)
'number by clumsy rob welcomed by sue from the west' is the wordplay.
'number' becomes 'ten' (ten is a kind of number).
'by' says to put letters next to each other.
'clumsy' is an anagram indicator.
'welcomed by' indicates putting letters inside (I've seen this in other clues).
'from the west' says the letters should be written in reverse.
'sue' written backwards gives 'eus'.
'rob' anagrammed gives 'bro'.
'bro' inserted inside 'eus' is 'ebrous'.
'ten'+'ebrous'='TENEBROUS'
(Other definitions for tenebrous that I've seen before include "Murky" , "Gloomy" .)