Helps when relative outwardly tires (7)
I believe the answer is:
assists
'helps' is the definition.
(assisting is a kind of helping)
'when relative outwardly tires' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'relative' becomes 'sis' (short for sister).
'outwardly' says to hollow out the word (remove centre letters) (only the outermost letters are used).
'tires' with its middle removed is 'ts'.
'as'+'sis'+'ts'='ASSISTS'
(Other definitions for assists that I've seen before include "Contributes to success" , "Helps or waits on" , "Lends a hand" , "Aids" , "Provides" .)