Lukewarm old rocker gets holy inside (5)
I believe the answer is:
tepid
'lukewarm' is the definition.
(I know this)
'old rocker gets holy inside' is the wordplay.
I cannot really understand how this works, but
'holy' could be 'pi' (I've seen this in other clues) and 'pi' is found in the answer.
'old rocker' could be 'ted' and 'ted' is located in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
(Other definitions for tepid that I've seen before include "Showing little interest or enthusiasm" , "What's a bit warm" , "Not very warm (water)" , "lacking enthusiasm" , "Slightly warm" .)