Pretty trifle makes graduate turn blue (6)
I believe the answer is:
bauble
'pretty trifle' is the definition.
'bauble' can be an answer for 'trifle' (I've seen this in another clue). I am unsure of the 'pretty' bit.
'graduate turn blue' is the wordplay.
'graduate' becomes 'BA' (someone with a Bachelor of Arts degree).
'turn' indicates anagramming the letters.
'blue' is an anagram of 'uble'.
'ba'+'uble'='BAUBLE'
'makes' is the link.
Can you help me to learn more?
(Other definitions for bauble that I've seen before include "Showy but valueless ornament" , "'Bead, trinket (6)'" , "Small cheap trinket" , "worthless D [DECORATION]" , "Showy trinket" .)