Stone to fail to gather moss - even at this pace? (6)
I believe the answer is:
stroll
'gather moss even at this pace?' is the definition.
'stroll' can be an answer for 'pace?' (I have seen 'gentle pace' mean 'stroll' so perhaps 'pace' could also mean 'stroll'). I am not certain of the rest of the definition.
'stone to fail' is the wordplay.
'stone' becomes 'st' (abbreviation).
'to fail' becomes 'roll' (I can't explain this - if you can you should give a lot more credence to this answer).
'st'+'roll'='STROLL'
'to' is the link.
Can you help me to learn more?
(Other definitions for stroll that I've seen before include "Promenade" , "Walk slowly and idly" , "cinch" , "Saunter in no particular direction" , "A casual or lazy walk" .)