Fuel problem keeps airmen fidgeting initially (8)
I believe the answer is:
paraffin
'fuel' is the definition.
(paraffin is a kind of fuel)
'problem keeps airmen fidgeting initially' is the wordplay.
'problem' becomes 'pain' (both can mean an inconvenience).
'keeps' indicates putting letters inside.
'airmen' becomes 'RAF' (Royal Air Force).
'initially' indicates taking the first letters.
The initial letter of 'fidgeting' is 'f'.
'raf'+'f'='raff'
'pain' going around 'raff' is 'PARAFFIN'.
(Other definitions for paraffin that I've seen before include "Possibly oil" , "Kerosene" , "Waxy flammable substance" , "Petroleum product" , "Fuel oil obtained from petroleum or coal" .)