Charlie too old for treatment (8)
I believe the answer is:
coverage
'for treatment' is the definition.
(I've seen this before)
'charlie too old' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet).
'too old' becomes 'overage' (I've seen this before).
'c'+'overage'='COVERAGE'
(Other definitions for coverage that I've seen before include "News reports" , "insurance" , "Press reporting" , "Commentary" , "Media reporting" .)