Cut down time in beach cabin at last (7)
I believe the answer is:
shorten
'cut down' is the definition.
(I know that cut down is a is a more specific form of the action of shorten)
'time in beach cabin at last' is the wordplay.
'time' becomes 't' (abbreviation).
'in' indicates putting letters inside.
'beach' becomes 'shore' (I've seen this before).
'at last' suggests the final letters.
The last letter of 'cabin' is 'n'.
't' placed into 'shore' is 'shorte'.
'shorte'+'n'='SHORTEN'
(Other definitions for shorten that I've seen before include "contract" , "Put extra fat" , "Clip" , "Curtail" , "Make less long" .)