Restless in Berlin, I start to yawn, nursing temperature (5)
I believe the answer is:
'restless' is the definition.
'in berlin i start to yawn nursing temperature' is the wordplay.
'in berlin i' becomes 'ich' ('I' in German).
'start to' says to take the initial letters.
'nursing' indicates putting letters inside.
'temperature' becomes 't' (abbreviation).
The first letter of 'yawn' is 'y'.
'ichy' placed around 't' is 'ITCHY'.
(Other definitions for itchy that I've seen before include "Affected by skin irritation", "Scratchy", "Bothersome", "Tickling", "Like the feet of the restless".)