Move in a way that's plumb vertical? (3)
I believe the answer is:
bob
This might be a double definition.
'move in a way' is the first definition.
'bob' can be an answer for 'move' (bobbing is a kind of moving). I am unsure of the 'in a way' bit.
'plumb vertical?' is the second definition.
'bob' can be an answer for 'plumb' (thesaurus). I'm not certain of the 'vertical?' bit.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for bob that I've seen before include "-- Dylan, singer" , "Old coin for Robert" , "Quick curtsy" , "Bounce" , "Change" .)