Magnificent second place finish I had (8)
'magnificent' is the definition.
('splendid' can be a synonym of 'magnificent')
'second place finish i had' is the wordplay.
'second' becomes 's' (common abbreviation).
'place' becomes 'pl' (I've seen this in other clues).
'finish' becomes 'end' ('end' can be a synonym of 'finish'**).
'i had' becomes 'id' (I'd).
(Other definitions for splendid that I've seen before include "Marvellous", "Great", "Magnificent, very impressive", "Very fine, quite glorioous", "Wicked".)