Field certain rugby players to defend unusual upset (7)
I believe the answer is:
paddock
'field' is the definition.
(I've seen this before)
'rugby players to defend unusual upset' is the wordplay.
'rugby players' becomes 'pack' (a rugby scrum is formed by two packs of players).
'to defend' indicates putting letters inside.
'unusual' becomes 'odd' (similar in meaning).
'upset' says the letters should be written in reverse.
'odd' backwards is 'ddo'.
'pack' placed around 'ddo' is 'PADDOCK'.
'certain' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for paddock that I've seen before include "Where horses are paraded before a race" , "Field, often for horses" , "Pen for horses" , "Small field for horses" , "Enclosure at racetrack for horses" .)