I've seent his clue before, also with no letter count so it is it a normal crossword clue? I think the definition is armchair(supporter) but think, if so, it's very weak
//lacking or not involving practical or direct experience of a particular subject or activity.
modifier noun: armchair; modifier noun: arm-chair
"an armchair traveller"//
still seems weak to me. I think of an amateur footballer as one who plays in the park or Sunday league rather than one who just watches from an armchair.