Work on small caber (4)
I believe the answer is:
slog
'work' is the definition.
(I know that slog is a more specific form of the action the work)
'on small caber' is the wordplay.
'on' says to put letters next to each other.
'small' becomes 's' (abbreviation - e.g. clothes size).
'caber' becomes 'log' (I can't explain this - if you can you should give a lot more credence to this answer).
's' put next to 'log' is 'SLOG'.
Can you help me to learn more?
(Other definitions for slog that I've seen before include "almighty wallop" , "Work (or walk) involving great effort" , "Hit hard - hard trek" , "Long tedious task" , "Walk hard carrying logs?" .)