It is put in by those who want a row (3)
I believe the answer is:
oar
This clue could be a double definition.
'it is put in by those who want' is the first definition.
The definition suggests a singular noun which matches the answer.
'a row' is the second definition.
(oar can mean to row with oars)
Can you help me to learn more?
(Other definitions for oar that I've seen before include "Propelling pole" , "Bladed implement" , "Crewman" , "Sweep" , "spoon?" .)