Canal build-up discovered behind decks, say (6)
I believe the answer is:
earwax
'canal' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'build-up discovered behind decks say' is the wordplay.
'build up' becomes 're-arm' (re-arming is a kind of building up).
'discovered' means to look at the middle letters (dis-covered - outer letters removed).
'behind decks say' becomes 'wax' (I am not sure about this - if you are sure you should believe this answer much more).
The central letters of 'rearm' are 'ear'.
'ear'+'wax'='EARWAX'
Can you help me to learn more?
(Other definitions for earwax that I've seen before include "Secretion that can impair hearing" , "Hearing problem" , "Substance accumulating in the lugholes" , "Secretion from aural glands" , "Shell-like secretion" .)