Jack may take Paul in (3)
I believe the answer is:
tar
This might be a double definition.
'jack' is the first definition.
(both are informal terms for sailor)
'take paul in' is the second definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'may' acts as a link.
Can you help me to learn more?
(Other definitions for tar that I've seen before include "Thick, black and sticky liquid" , "Sailor; road surface" , "Informal sailor or road surfacing material" , "Informal sailor or coal distillation" , "Sailor (colloq.)" .)