Only a fathead can keep baby quiet! (5)
I believe the answer is:
dummy
'baby quiet' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for dummy that I've seen before include "Make as if to pass" , "that all the players can see" , "who lays his cards on the table?" , "Bridge hand on table" , "Mock-up; non-working version" .)