The first decaying way to be reliable (6)
I believe the answer is:
trusty
'be reliable' is the definition.
(associated in meaning)
'the first decaying way' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'way' could be 'st' (abbreviation for street) and 'st' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for trusty that I've seen before include "Reliable, honest and firm" , "Reliable, faithful" , "Dependable" , "Reliable, well-behaved prisoners with privileges" , "Staunch" .)