Toga's tricky to pin around the stomach (7)
I believe the answer is:
gastric
'the stomach' is the definition.
(gastric means relating to the stomach)
'toga's tricky to pin around' is the wordplay.
'around' says the answer is hidden in the clue.
'GASTRIC' is hidden in the letters of 'togas tricky pin'.
(Other definitions for gastric that I've seen before include "touching stomach" , "Pertaining to the stomach" , "Abdominal" , "of the corporation?" , "Stomachic" .)