Stress it runs in the family (6)
I believe the answer is:
strain
'stress' is the definition.
(I know that stress can be written as strain)
'it runs in the family' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'runs' becomes 'r' (cricket abbreviation).
'in the' is an insertion indicator.
'family' becomes 'sain' (I am not sure about this - if you are sure you should believe this answer much more).
't'+'r'='tr'
'tr' placed within 'sain' is 'STRAIN'.
Can you help me to learn more?
(Other definitions for strain that I've seen before include "making a great demand on the emotions?" , "Pass through a colander" , "Tension - tune" , "Filter - intense effort" , "Pressure - filter" .)