Exercises twice before unwrapping rich digestive (6)
I believe the answer is:
peptic
'digestive' is the definition.
(I've seen this in another clue)
'exercises twice before unwrapping rich' is the wordplay.
'exercises twice' can mean two replacements for 'exercises'.
'exercises' becomes 'pe' (Physical Education).
'exercises' becomes 'PT' (Physical Training).
'before' says to put letters next to each other.
'unwrapping' means to look at the middle letters (letters which 'wrap' the word are removed).
The centre of 'rich' is 'ic'.
'pe'+'pt'+'ic'='PEPTIC'
(Other definitions for peptic that I've seen before include "of the digestive system" , "Of digestion, and a related ulcer" , "Relating to digestion - kind of ulcer" , "Kind of ulcer in stomech or duodenum" , "This ulcer is in the stomach or duodenum" .)