Sped with pen in further test after turning calmer (13)
I believe the answer is:
tranquilliser
'calmer' is the definition.
(I've seen this before)
'sped with pen in further test after turning' is the wordplay.
I cannot quite understand how this works, but
'sped' could be 'ran' (running is a kind of speeding) and 'ran' is found in the answer.
'pen' could be 'quill' (quill is a kind of pen) and 'quill' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tranquilliser that I've seen before include "Calming drug" , "Sedative" , "Calmer" , "Calming-down drug" , "Pill used to calm" .)