Rod's line snagged in spleen? (6)
I believe the answer is:
angler
'rod's' is the definition.
(rod can mean an angler)
'line snagged in spleen?' is the wordplay.
'line' becomes 'l' (used when specifying particular lines from a poem).
'snagged in' means one lot of letters goes inside another (inserted letters are caught or snagged).
'spleen?' becomes 'anger' (I've seen this in another clue).
'l' going into 'anger' is 'ANGLER'.
(Other definitions for angler that I've seen before include "Isaac Walton wrote of the 'Compleat' one" , "Sportsman" , "I cast Rod" , "Walton's was Compleat" , "A rod and line fisherman" .)