One might make quack medic rankle periodically (5)
I believe the answer is:
drake
'one might make quack' is the definition.
I can't tell whether this definition defines the answer.
'medic rankle periodically' is the wordplay.
'medic' becomes 'dr' (abbreviation for doctor).
'periodically' means one should take alternating letters (letters must be selected 'every so often').
The alternate letters of 'rankle' are 'ake'.
'dr'+'ake'='DRAKE'
Can you help me to learn more?
(Other definitions for drake that I've seen before include "might be after a duck?" , "Sir Francis - -" , "one at home on the water" , "Hoe user" , "Aquatic bird" .)