Alternatively have a paddle (3)
I believe the answer is:
oar
'paddle' is the definition.
(I've seen this in another clue)
'alternatively have a' is the wordplay.
'alternatively' becomes 'or'.
'have' is an insertion indicator.
'or' going around 'a' is 'OAR'.
(Other definitions for oar that I've seen before include "Propelling pole" , "Sweep" , "It ends in blade" , "propellor" , "Boat propellant" .)