In prison, heart's uplifted by a stringed instrument (5)
I believe the answer is:
sitar
'stringed instrument' is the definition.
(I know that sitar is a type of stringed instrument)
'in prison heart's uplifted by a' is the wordplay.
'in prison' becomes 'inside' (I've seen this before).
'heart's' indicates the central letters (I've seen 'heart of' mean this).
'uplifted' says the letters should be written backwards.
'by a' becomes 'rat' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The centre of 'inside' is 'si'.
'rat' backwards is 'tar'.
'si'+'tar'='SITAR'
Can you help me to learn more?
(Other definitions for sitar that I've seen before include "Hindu string instrument" , "Astir with Indian long-necked lute" , "Indian stringed instrument" , "Plucked instrument" , "music producer" .)