Tent was initially of poor quality fabric (5)
I believe the answer is:
twill
'fabric' is the definition.
(twill is a kind of fabric)
'tent was initially of poor quality' is the wordplay.
'initially' says to take the initial letters.
'of poor quality' becomes 'ill'.
The first letters of 'tent was' is 'tw'.
'tw'+'ill'='TWILL'
(Other definitions for twill that I've seen before include "Diagonal-weave fabric" , "Fabric woven to produce a surface of diagonal parallel ridges" , "Strong ridged fabric" , "Fabric with distinctive weave" , "Fabric weave with parallel diagonal lines" .)