Soccer medico finding no source for loud tick after turning round? (6)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

[n] OISY (loud) without the first letter (source), then HP (abbreviation for hire purchase = “tick” in slang = buying goods on credit), all reversed (after turning round). Short for physiotherapist; term often used for someone employed to help footballers or other sportspeople with injuries.