Get to the bottom of (6)
'get to the bottom of' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for fathom that I've seen before include "Measure of depth, 6 ft." , "Six-foot measure" , "Nautical measure of six feet" , "Six feet in depth; grasp" , "Nautical measure of depth" .)
'get to the bottom of' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for unravel that I've seen before include "Straighten out" , "Disentangle knitted wool or solve mystery" , "Become undone" , "Unpick, untangle" , "Solve the problem" .)