Scarcity of jobs ultimately behind poor earners (8)
I believe the answer is:
rareness
'scarcity' is the definition.
(rareness is a kind of scarcity)
'jobs ultimately behind poor earners' is the wordplay.
'ultimately' says to take the final letters.
'behind' is a charade indicator (letters next to each other).
'poor' is an anagram indicator.
The final letter of 'jobs' is 's'.
'earners' anagrammed gives 'rarenes'.
's' after 'rarenes' is 'RARENESS'.
'of' acts as a link.
(Other definitions for rareness that I've seen before include "Unusual quality" , "Scarcity" , "State of being uncommon or very scarce" , "Uncommon quality" .)