Mother runs after colleague (5)
I believe the answer is:
mater
'mother' is the definition.
(old-fashioned term for mother)
'runs after colleague' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'after' is a charade indicator (letters next to each other).
'colleague' becomes 'mate'.
'r' after 'mate' is 'MATER'.
(Other definitions for mater that I've seen before include "having children" , "mum's the word" , "Dam" , "An old Roman mother" , "Mother (Latin or old slang)" .)