Pitch checker's routine nap disturbed (5,5)
I believe the answer is:
piano tuner
'pitch checker's' is the definition.
(a piano tuner checks the pitch of keys)
'routine nap disturbed' is the wordplay.
'disturbed' indicates an anagram (the order of letters is disturbed).
'routine'+'nap'='routinenap'
'routinenap' with letters rearranged gives 'PIANO TUNER'.
(Other definitions for piano tuner that I've seen before include "Grand adjuster?" , "one with a fine ear?" , "Instrument adjuster" .)