A defender taken by surprise (5)
I believe the answer is:
aback
'by surprise' is the definition.
(I've seen this in another clue)
'a defender' is the wordplay.
'defender' becomes 'back' (I've seen this before).
'a'+'back'='ABACK'
'taken' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for aback that I've seen before include "(Taken) by surprise" , "One is surprised when taken thus" , "dismayed to be taken thus?" , "Sternwards" , "To take someone -- is to surprise them" .)