Unable to feel American casualty's digits? (7)
I believe the answer is:
numbers
'digits?' is the definition.
(digit is a kind of number)
'unable to feel american casualty's' is the wordplay.
I cannot really see how this works, but
'feel' could be 'be' and 'be' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for numbers that I've seen before include "Integers" , "anaesthetists?" , "Fourth OT book - figures" , "Biblical book - anaesthetics" , "OT Book 4" .)