Remove contents of round tower (3)
I believe the answer is:
tug
'tower' is the definition.
(something that tows)
'remove contents of round' is the wordplay.
'remove contents' becomes 'gut'.
'of round' is a reversal indicator (I've seen 'round' mean this).
'gut' back-to-front is 'TUG'.
(Other definitions for tug that I've seen before include "Pull a form of boat" , "Tow boat" , "Pull sharply" , "A sharp pull or a towing boat" , "Boat to pull larger one" .)