Picking it was a ropy job (5)
I believe the answer is:
oakum
This could be a double definition.
'picking' is the first definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'it was a ropy job' is the second definition.
The definition suggests a singular noun which matches the answer.
Can you help me to learn more?
(Other definitions for oakum that I've seen before include "Tarred rope" , "Tarred ropes teased out for caulking ships" , "Caulking material" , "What convicts used to pick" , "Rope fibre for caulking wooden ships" .)