"Isolate"

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: SEGREGATE | Definition: 'Isolate' | Wordplay: charade of S (small) + EGRE[t] (wader, scratching back) + GATE (barrier)