Protection provided by extremely dependable guard (7)
I believe the answer is:
defence
'protection' is the definition.
(defence is a kind of protection)
'by extremely dependable guard' is the wordplay.
'by' says to put letters next to each other.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'guard' becomes 'fence' (guard can mean a protective fence).
'dependable' with its centre taken out is 'de'.
'de' put next to 'fence' is 'DEFENCE'.
'provided' acts as a link.
(Other definitions for defence that I've seen before include "The D in MoD" , "Act of keeping safe from danger" , "Military's purpose" , "Armed forces' role" , "shelter" .)