. . . or last course of little value?
I believe the answer is:
trifle
'course of little value?' is the definition.
'trifle' can be an answer for 'course' (trifle is a kind of course). I'm unsure of the 'of little value?' bit.
'or last' is the wordplay.
I cannot really understand how this works, but
'last' could be 't' (I've seen this in other clues) and 't' is found in the answer.
The remaining letters 'rifle' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for trifle that I've seen before include "Dessert - something unimportant" , "Cold dessert" , "Dessert; act frivolously" , "Filter (anag.)" , "Possible component of meal" .)