Maroons a musical group on first of September (8)
'maroons' is the definition.
The definition and answer can be both to do with ownership as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?
'a musical group on first of september' is the wordplay.
'musical group' becomes 'band' (band is a kind of musical group).
'first of september' becomes 's' (1st letter of 'september').
Can you help me to learn more?
(Other definitions for abandons that I've seen before include "Forsake, leave behind", "Deserts, say a sinking ship", "Forsakes, leaves behind", "Deserts, forsakes", "Deserts, gives up completely".)