Consume a bit of life in US city with aplomb (6)
I believe the answer is:
neatly
'with aplomb' is the definition.
'consume a bit of life in us city' is the wordplay.
'consume' becomes 'eat' (eating is a kind of consuming).
'a bit of' indicates taking the first letters.
'in' is an insertion indicator.
'us city' becomes 'ny' (I've seen this in other clues**).
The first letter of 'life' is 'l'.
'eat'+'l'='eatl'
'eatl' put within 'ny' is 'NEATLY'.
(Other definitions for neatly that I've seen before include "Tidily and cleanly" , "Orderly and cleanly" , "In tidy fashion" , "'Tidily, trimly (6)'" , "nicely" .)