Only (4)
'only' is the definition.
(I know that only can be written as lone)
This is the entire clue.
(Other definitions for lone that I've seen before include "Unaccompanied" , "The ... Ranger, fictional masked cowboy" , "He likes to operate by himself" , "Solitary, without companions" , "Solitary or single" .)
'only' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for mere that I've seen before include "Lake, pond (poetic)" , "Pure; lake" , "Simply, nothing more than" , "Just an English lake" , "Pond - pure and simple" .)
'only' is the definition.
(I know that only can be written as sole)
This is the entire clue.
(Other definitions for sole that I've seen before include "Flatfish; exclusive" , "fish in the sea!" , "Just one - fish" , "Lone; part of foot" , "Dover - -" .)
'only' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for just that I've seen before include "Ethically right" , "free from bias" , "Fair and reasonable" , "Barely - deserved" , "Exactly" .)
'only' is the definition.
(merely can mean only or simply)
This is the entire clue.
(Other definitions for merely that I've seen before include "'Only, and nothing more (6)'" , "Simply - only" , "Just one" .)