A bit deranged for a time (3)
I believe the answer is:
'a time' is the definition.
(era is a kind of time)
'a bit deranged for' is the wordplay.
'a bit' indicates the answer is hidden within the clue (the answer is formed by a bit of the clue).
'ERA' is hidden in the letters of 'deranged for'.
(Other definitions for era that I've seen before include "Important historical period" , "Eon" , "Cycle" , "Distinctive period of time" , "Geological period" .)