Different parent loses head (5)
I believe the answer is:
other
'different' is the definition.
(similar in meaning)
'parent loses head' is the wordplay.
'parent' becomes 'mother' (type of parent).
'loses head' means to remove the first letter.
'mother' with its initial letter taken off is 'OTHER'.
(Other definitions for other that I've seen before include "Different (from those mentioned)" , "Different, alternative" , "Different, not the same one or this one" , "Remaining" , "not like you" .)