Quarreling β or turning up on side (6)
I believe the answer is:
rowing
'quarreling' is the definition.
Although both the answer and definition are present participle verbs, I don't understand how one could define the other.
'or turning up on side' is the wordplay.
'turning up' is a reversal indicator.
'on' says to put letters next to each other.
'side' becomes 'wing' (as in left and right wings).
'or' back-to-front is 'ro'.
'ro'+'wing'='ROWING'
Can you help me to learn more?
(Other definitions for rowing that I've seen before include "in dispute" , "Propelling boat with oars" , "Sport associated with Henley" , "Aquatic sport" , "Sculling sport?" .)