Doctor in Welshman heading for Swansea for remedy (7)
I believe the answer is:
redress
'for remedy' is the definition.
(synonyms)
'doctor in welshman heading for swansea' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'in' indicates putting letters inside.
'welshman' becomes 'rees' (common Welsh surname).
'heading for' says to take the initial letters.
The initial letter of 'swansea' is 's'.
'dr' put inside 'rees' is 'redres'.
'redres'+'s'='REDRESS'
(Other definitions for redress that I've seen before include "Put right" , "Get back into gear" , "set straight again" , "Correct" , "Set right - compensation" .)