Pitiful, heartless — reform required to give boost (6)
I believe the answer is:
uplift
'boost' is the definition.
(I've seen this before)
'pitiful heartless reform' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'reform' indicates anagramming the letters (letters in a new form).
'pitiful' with its middle removed is 'pitful'.
'pitful' anagrammed gives 'UPLIFT'.
'required to give' acts as a link.
(Other definitions for uplift that I've seen before include "Boost" , "Elevation (of the spirit)" , "Inspire or raise" , "Act of raising" , "Increase; moral elevation" .)