Family diagrams omit school science (10)
I believe the answer is:
kinematics
'science' is the definition.
(kinematics is a kind of science)
'family diagrams omit school' is the wordplay.
I cannot really understand how this works, but
'family' could be 'kin' (synonyms) and 'kin' is found in the answer.
'school' could be 's' and 's' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for kinematics that I've seen is " Some mechanics".)