Suitor runs after love in agony (5)
I believe the answer is:
wooer
'suitor' is the definition.
(synonyms)
'runs after love in agony' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'after' means one lot of letters go next to another.
'love' becomes 'o' (love means zero in tennis).
'in' is an insertion indicator.
'agony' becomes 'woe' (I've seen this in another clue).
'o' going inside 'woe' is 'wooe'.
'r' after 'wooe' is 'WOOER'.
(Other definitions for wooer that I've seen before include "person to court" , "Romantic type" , "One courting" , "One who goes to court" , "Suitor" .)