Getting on, close to bedtime, steeped in a liquor with strong base (6)
I believe the answer is:
ageing
'getting on' is the definition.
('age' can be a synonym of 'get on')
'close to bedtime steeped in a liquor with strong base' is the wordplay.
'close to' suggests the final letters (the 'close' to the word).
'steeped in' is an insertion indicator (I've seen this in other clues).
'liquor' becomes 'gin' (gin is a kind of liquor).
'with' says to put letters next to each other.
'base' suggests the final letters (the base of the word).
The final letter of 'bedtime' is 'e'.
The last letter of 'strong' is 'g'.
'a'+'gin'='agin'
'e' placed into 'agin' is 'agein'.
'agein'+'g'='AGEING'
(Other definitions for ageing that I've seen before include "Getting old" , "Elderly" , "Getting older" , "no longer fresh" , "getting more advanced?" .)