Tries unsuccessfully to take test anew (5)
I believe the answer is:
resit
'test anew' is the definition.
'resit' can be an answer for 'test' (I have seen 'Second test' mean 'resit' so perhaps 'test' could also mean 'resit'). I'm not sure about the 'anew' bit.
'tries unsuccessfully to' is the wordplay.
'tries' anagrams to 'RESIT'.
However, I'm unsure how this is indicated.
'take' acts as a link.
Can you help me to learn more?
(Other definitions for resit that I've seen before include "take another exam" , "later exam" , "Take examination again" , "second exam" , "repeated test" .)