Gas, even a bit reduced, just delivered (8)
I believe the answer is:
neonatal
'just delivered' is the definition.
(I've seen this before)
'gas even a bit reduced' is the wordplay.
'gas' becomes 'neon' (neon is a gas).
'even a bit' becomes 'at all' (I've seen this in another clue).
'reduced' means to remove the last letter.
'atall' with its last letter taken off is 'atal'.
'neon'+'atal'='NEONATAL'
(Other definitions for neonatal that I've seen before include "Relating to new baby" , "Of or for the newly born" , "Describing newly-born" , "Recently delivered" , "at a very young age" .)