Doctor helps to restrain a second unfortunate (7)
I believe the answer is:
hapless
'unfortunate' is the definition.
('hapless' can be similar in meaning to 'unfortunate')
'doctor helps to restrain a second' is the wordplay.
'doctor' indicates an anagram.
'to restrain' indicates putting letters inside.
'second' becomes 's' (common abbreviation).
'helps' is an anagram of 'hples'.
'hples' placed around 'a' is 'haples'.
'haples'+'s'='HAPLESS'
(Other definitions for hapless that I've seen before include "Ill-fated" , "Pathetic" , "Ill-starred" , "Piteous" , "Unfortunate, wretched" .)