Grim face of stranded flyer (5)
I believe the answer is:
stern
'grim' is the definition.
(I know that grim can be written as stern)
'face of stranded flyer' is the wordplay.
'face of' indicates taking the first letters.
'flyer' becomes 'tern'.
The first letter of 'stranded' is 's'.
's'+'tern'='STERN'
(Other definitions for stern that I've seen before include "Tail of a beagle" , "having a forbidding appearance" , "Unsmiling" , "Severe -- back of boat" , "Rents out at rear of boat" .)