Mouth making daughter terribly late (5)
I believe the answer is:
delta
'mouth' is the definition.
(I've seen this before)
'daughter terribly late' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'terribly' indicates anagramming the letters.
'late' anagrammed gives 'elta'.
'd'+'elta'='DELTA'
'making' acts as a link.
(Other definitions for delta that I've seen before include "Foreign character" , "Fourth Greek letter? - area at river mouth" , "Divided river outlet" , "Eg, outlet of the Nile" , "Area of distributaries in a river basin" .)