Drink it when reflecting in the morning air (3,5)
I believe the answer is:
tia maria
'drink' is the definition.
(tia maria is an alcoholic drink)
'it when reflecting in the morning air' is the wordplay.
'when reflecting' shows that the letters should be reversed in order.
'in the morning' becomes 'am' (short for ante meridiem - before noon).
'air' becomes 'aria' (I've seen this in another clue).
'it' written backwards gives 'ti'.
'ti'+'am'+'aria'='TIA MARIA'
(Other definitions for tia maria that I've seen before include "Coffee-flavoured trademarked liqueur" , "Coffee-flavoured rum drink" , "After-dinner liqueur" , "Coffee-flavour liqueur" , "drink is served?" .)