Starts to serve tea with green drinking-tube (5)
I believe the answer is:
straw
'tube' is the definition.
(I know that straw is a type of tube)
'starts to serve tea with green' is the wordplay.
'starts to' indicates taking the first letters.
'with' means one lot of letters go next to another.
'green' becomes 'raw' (both can mean naive or inexperienced).
The first letters of 'serve tea' is 'st'.
'st'+'raw'='STRAW'
'drinking' acts as a link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for straw that I've seen before include "Plant fibre used as fodder" , "Dried stalks; yellow" , "Pale yellow colour" , "Disastrously, it may be the last" , "remnant of harvest" .)