Hooligan initially hiding in towing vessel (4)
I believe the answer is:
thug
'hooligan' is the definition.
(I've seen this before)
'initially hiding in towing vessel' is the wordplay.
'initially' suggests taking the first letters.
'in' indicates putting letters inside.
'towing vessel' becomes 'tug' (I've seen this before).
The initial letter of 'hiding' is 'h'.
'h' put into 'tug' is 'THUG'.
(Other definitions for thug that I've seen before include "Rough" , "Hood" , "Burrowing crustacean" , "Heavy" , "violent gang member" .)