Get to the bottom of (7)
I believe the answer is:
unravel
'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 "Solve the problem" , "Disentangle knitted wool or solve mystery" , "Sort out" , "Come undone; solve" , "Make sense of" .)