European politician initially helping a sibling showing stress (8)
I believe the answer is:
emphasis
'stress' is the definition.
(I know that stress can be written as emphasis)
'european politician initially helping a sibling' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'politician' becomes 'MP' (Member of Parliament).
'initially' indicates taking the first letters.
'sibling' becomes 'sis' (short for sister).
The first letter of 'helping' is 'h'.
'e'+'mp'+'h'+'a'+'sis'='EMPHASIS'
'showing' acts as a link.
(Other definitions for emphasis that I've seen before include "Stress, accent" , "Stress, accentuation" , "Stress or significance" , "Force" , "Stress - misshape (anag)" .)