Tailor's initial choice fabric (5)
I believe the answer is:
twill
'fabric' is the definition.
(type of fabric)
'tailor's initial choice' is the wordplay.
'initial' suggests taking the first letters.
'choice' becomes 'will' (someone's will is their decision or choice).
The first letter of 'tailors' is 't'.
't'+'will'='TWILL'
(Other definitions for twill that I've seen before include "Stuff" , "Strong ridged fabric" , "Fabric weave with parallel diagonal lines" , "Strong woven fabric" , "Cloth with diagonal ribs" .)