Very soon joining trendy pair of smoothies (2,3,6)
I believe the answer is:
in two shakes
'very soon' is the definition.
I know nothing about this answer so I can't tell whether this works.
'joining trendy pair of smoothies' is the wordplay.
'joining' says to put letters next to each other.
'trendy' becomes 'in' ('in' can mean fashionable).
'pair' becomes 'two' (I've seen this in another clue).
'of smoothies' becomes 'shakes' (I can't explain this - if you can you should believe this answer much more).
'in' next to 'two' is 'intwo'.
'intwo'+'shakes'='IN TWO SHAKES'
Can you help me to learn more?
(Another definition for in two shakes that I've seen is " Quickly".)