At some stage, a novice will fall behind (3)
I believe the answer is:
lag
'fall behind' is the definition.
(synonyms)
'at some stage a novice' is the wordplay.
'at' means one lot of letters go next to another.
'some' becomes 'a'.
'stage' becomes 'g' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a novice' becomes 'L' (as in a learner driver with L-plates on their car).
'a'+'g'='ag'
'ag' put after 'l' is 'LAG'.
'will' is the link.
Can you help me to learn more?
(Other definitions for lag that I've seen before include "Fall behind or cover to prevent heat loss" , "Protect from cold" , "Drag one's feet" , "Cover pipes" , "Ex-convict" .)