Hat material, international (5,3)
I believe the answer is:
cloth cap
'hat' is the definition.
(I have seen 'Flat hat ' mean 'cloth cap' so perhaps 'hat' could also mean 'cloth cap')
'material international' is the wordplay.
'material' becomes 'cloth' (synonyms).
'international' becomes 'cap' (sportsperson who competes internationally).
'cloth'+'cap'='CLOTH CAP'
(Other definitions for cloth cap that I've seen before include "Flat hat" , "Flat headgear" , "Stereotypical headgear for the working classes" .)