Portable for a distance, getting round Beachy Head (6)
I believe the answer is:
mobile
'portable' is the definition.
(I've seen this before)
'distance getting round beachy head' is the wordplay.
'distance' becomes 'mile' (mile is a unit of distance).
'getting round' indicates putting letters inside.
'beachy head' becomes 'ob' (I am not sure about this - if you are sure you should believe this answer much more).
'mile' going around 'ob' is 'MOBILE'.
'for a' is the link.
Can you help me to learn more?
(Other definitions for mobile that I've seen before include "With freedom of movement" , "Able to move, not fixed" , "Telephone" , "Moveable, phone say" , "Moving" .)