Lower payment? (3)
I believe the answer is:
sub
I believe this is a double definition.
'lower' is the first definition.
(thesaurus)
'payment?' is the second definition.
(I have seen 'Advance payment ' mean 'sub' so perhaps 'payment' could also mean 'sub')
(Other definitions for sub that I've seen before include "Underwater craft" , "Underwater boat" , "Prefix meaning beneath" , "Junior editor" , "Prefix denoting under" .)