Scan book series by Sartre, losing heart (6)
I believe the answer is:
browse
'scan' is the definition.
(thesaurus)
'book series by sartre losing heart' is the wordplay.
'book' becomes 'b'.
'series' becomes 'row' (I've seen this before).
'by' means one lot of letters go next to another.
'losing heart' says to hollow out the word (remove centre letters).
'sartre' with its middle removed is 'se'.
'b'+'row'+'se'='BROWSE'
(Other definitions for browse that I've seen before include "Read idly" , "Graze - glance through a book, magazine etc" , "Surf (the Internet)" , "Leaf through (a book)" , "Look through in a random way, a book or shop, say" .)