More trouble, billions missing (5)
I believe the answer is:
other
'more' is the definition.
(synonyms)
'trouble billions missing' is the wordplay.
'trouble' becomes 'bother' (synonyms).
'billions' becomes 'b'.
'missing' indicates named letters should be taken away.
'bother' with 'b' taken away is 'OTHER'.
(Other definitions for other that I've seen before include "else!" , "Alternative of two" , "Different, disparate" , "Different; alternate" , "Throe (anag)" .)