Old commander, on another occasion, dropping in (3)
I believe the answer is:
aga
'old commander' is the definition.
(historical Muslim military commander)
'on another occasion dropping in' is the wordplay.
'on another occasion' becomes 'again'.
'dropping' is a deletion indicator.
'again' with 'in' taken away is 'AGA'.
(Other definitions for aga that I've seen before include "--- Khan, spiritual head of Ismaili Muslims" , "Eastern leader" , "Palindromic Muslim title, as for Khan" , "In Turkey, an official" , "of the 17 [KITCHEN]" .)