Commander’s once more dropping in (3)
I believe the answer is:
aga
'commander's' is the definition.
(I've seen this before)
'once more dropping in' is the wordplay.
'once more' becomes 'again' (synonyms).
'dropping' suggests deleting specific letters.
'again' with 'in' taken away is 'AGA'.
(Other definitions for aga that I've seen before include "Proprietary name for a domestic stove" , "Kitchen stove" , "Kitchen range" , "Large iron stove" , "Muslim title and cooking stove" .)