Harry on the guitar (4)
I believe the answer is:
fret
'harry' is the definition.
(thesaurus)
'on the guitar' is the wordplay.
I cannot quite see how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is located in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
A single letter 'f' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for fret that I've seen before include "Be always anxious" , "Fog" , "Sort of saw work" , "Worry; wet mist" , "Worry about doing woodwork?" .)