Peak time, middle of work (3)
I believe the answer is:
tor
'peak' is the definition.
(a tor is a rocky peak)
'time middle of work' is the wordplay.
'time' becomes 't' (abbreviation).
'middle of' means to look at the middle letters.
The middle letters of 'work' are 'or'.
't'+'or'='TOR'
(Other definitions for tor that I've seen before include "Rot about the rocky height" , "High, rocky, bare hill" , "Fermenting agent" , "Pillar of rock" , "fell" .)