Langdon's heart captured by desperate lament (5)
I believe the answer is:
dirge
'lament' is the definition.
(synonyms)
'langdon's heart captured by desperate' is the wordplay.
'heart' indicates the central letters.
'captured by' is an insertion indicator.
'desperate' becomes 'dire' (I've seen this before).
The middle of 'langdon' is 'g'.
'g' placed inside 'dire' is 'DIRGE'.
(Other definitions for dirge that I've seen before include "Keen; lament" , "Funeral lament" , "Funeral hymn" , "Song or hymn of mourning" , "Funereal song" .)