When son, before noon, requires tea (5)
I believe the answer is:
assam
'tea' is the definition.
(I've seen this before)
'when son before noon' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'son' becomes 's' (genealogical abbreviation for son).
'before noon' becomes 'am' (as in AM on a clock).
'as'+'s'+'am'='ASSAM'
'requires' acts as a link.
(Other definitions for assam that I've seen before include "An Indian part" , "Variety of tea" , "NE Indian state (tea)" , "Tea state of India" , "brew?" .)