Feeble, as an excuse (4)
I believe the answer is:
lame
'feeble as an excuse' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lame that I've seen before include "Flimsy, as an excuse" , "game" , "Imperfect - material" , "Crippled" , "(Of an excuse) unconvincingly feeble" .)