Airmen flying in aerobatics initially showing fibre (6)
I believe the answer is:
raffia
'fibre' is the definition.
(raffia is a kind of fibre)
'airmen flying in aerobatics initially' is the wordplay.
'airmen' becomes 'raf'.
'initially' indicates taking the first letters.
The first letters of 'flying in aerobatics' is 'fia'.
'raf'+'fia'='RAFFIA'
'showing' acts as a link.
(Other definitions for raffia that I've seen before include "grass" , "Fibre from palm tree, used to make mats" , "Type of palm tree" , "that's seen at evening classes" , "a Madagascan basket-maker" .)