Though monotonous, it's arguably groovy (3)
I believe the answer is:
rut
'arguably groovy' is the definition.
I can't tell whether this defines the answer.
'though monotonous it's' is the wordplay.
'though monotonous' becomes 'ru' (I can't justify this - if you can you should give a lot more credence to this answer).
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'ru'+'t'='RUT'
Can you help me to learn more?
(Other definitions for rut that I've seen before include "animal passion" , "Pothole" , "Road depression, difficult to get out of" , "occupying male deer in autumn" , "Groove worn in surface" .)