Old footballer welcomes doctor and swallows drug for healing process (3,4)
I believe the answer is:
bed rest
'healing process' is the definition.
The definition suggests a singular noun which matches the answer.
'old footballer welcomes doctor and swallows drug' is the wordplay.
I cannot quite see how this works, but
'doctor' could be 'dr' (abbreviation) and 'dr' is present in the answer.
'drug' could be 'e' (E is another name for ecstasy) and 'e' is found in the answer.
'footballer' could be 'best' (George Best) and 'best' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'for' acts as a link.
Can you help me to learn more?
(Another definition for bed rest that I've seen is " sort of treatment".)