Poem on breaking Freyja's heart (5)
I believe the answer is:
elegy
'poem' is the definition.
(elegy is a kind of poem)
'on breaking freyja's heart' is the wordplay.
'on' becomes 'leg' (cricket term, fielding positions**).
'breaking' indicates putting letters inside.
'heart' indicates the central letters.
The middle letters of 'freyja' are 'ey'.
'leg' going inside 'ey' is 'ELEGY'.
(Other definitions for elegy that I've seen before include "Milton's Lycidas?" , "Song of lament" , "Poetic lament for the dead" , "Poem as Gray's in churchyard" , "Sad or reflective poem" .)