Plant where solitary workman at last relieved (4)
I believe the answer is:
aloe
'plant' is the definition.
(aloe is a kind of plant)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for aloe that I've seen before include "Fleshy-leaved plant" , "Bitter fruit" , "has a bitter taste" , "Plant source of purgative drug" , ". . . . vera, soothing plant" .)