Too controlled to be a failure (4-3)
I believe the answer is:
also-ran
'a failure' is the definition.
(I've seen this before)
'too controlled' is the wordplay.
'too' becomes 'also' (synonyms).
'controlled' becomes 'ran' (I've seen this in other clues).
'also'+'ran'='ALSO-RAN'
'to be' is the link.
(Other definitions for also-ran that I've seen before include "Non-winning horse" , "Not among the first three in race" , "Unplaced racehorse" , "Not placed in first three finishers" , "Non-winner in race" .)