Alternatively returning to find a merciless character wandering around (7)
I believe the answer is:
roaming
'wandering around' is the definition.
(I've seen this in another clue)
'alternatively returning to find a merciless character' is the wordplay.
'alternatively' becomes 'or'.
'returning' says the letters should be written backwards.
'to find' says to put letters next to each other.
'merciless character' becomes 'ming' (I've seen this in another clue).
'or' backwards is 'ro'.
'ro'+'a'+'ming'='ROAMING'
(Other definitions for roaming that I've seen before include "Ranging widely" , "wandering around" , "Moving about" , "Using a mobile on another network" , "Roving" .)