Look at the start or end of the clue

This is a reversal clue - look for indicators like 'back', 'returned', 'up' (in down clues), or 'west' (in across clues)

Join the wordplay parts together in sequence

Answer: KNEE | Wordplay: Strike a blow to groin having struck backside previously? (4)The “backside” of strucK + NEE (previously, as in a maiden name)