When abroad, use phone with nothing in memory (4)
I believe the answer is:
roam
'when abroad use phone' is the definition.
(to use a different phone network when abroad)
'nothing in memory' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'in' is an insertion indicator.
'memory' becomes 'ram' (RAM is an example).
'o' placed into 'ram' is 'ROAM'.
'with' is the link.
(Other definitions for roam that I've seen before include "Ramble without purpose" , "Wander widely" , "Prowl" , "range" , "Peregrinate" .)