Unknown place started to be reliable (6)
I believe the answer is:
steady
'be reliable' is the definition.
(I've seen this in another clue)
'unknown place started' is the wordplay.
I cannot quite understand how this works, but
'unknown' could be 'y' (algebra) and 'y' is present in the answer.
'place' could be 'stead' (synonyms) and 'stead' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'to' acts as a link.
Can you help me to learn more?
(Other definitions for steady that I've seen before include "Reliable - not shifting" , "Regular; firmly fixed" , "date seen regularly" , "Regular and reliable" , "Dependable; unmoving" .)