Its mate goes off occasionally (2,5)
I believe the answer is:
at times
'occasionally' is the definition.
(I've seen this before)
'its mate goes off' is the wordplay.
'goes off' indicates anagramming the letters.
'its'+'mate'='itsmate'
'itsmate' anagrammed gives 'AT TIMES'.
(Other definitions for at times that I've seen before include "employed by paper?" , "Occasionally" , "on some occasions" , "In the office" , "Where some journalists work" .)