A French channel not to be relied on (7)
I believe the answer is:
unsound
'not to be relied on' is the definition.
I can't tell whether this definition defines the answer.
'a french channel' is the wordplay.
'a french' becomes 'un' ('a' in French).
'channel' becomes 'sound' (synonyms).
'un'+'sound'='UNSOUND'
Can you help me to learn more?
(Other definitions for unsound that I've seen before include "Lame" , "Unfit or unreliable" , "Defective or flawed" , "silence?" , "Not strong or free from defect - perhaps evidence in court" .)