Desire being right inside grotto (5)
I believe the answer is:
crave
'desire' is the definition.
(I know that crave is a more specific form of the action desire)
'right inside grotto' is the wordplay.
'right' becomes 'r' (common abbreviation).
'inside' indicates putting letters inside.
'grotto' becomes 'cave' (I've seen this in another clue).
'r' placed inside 'cave' is 'CRAVE'.
'being' acts as a link.
(Other definitions for crave that I've seen before include "Really want" , "Lust after" , "Yearn for (something)" , "need, desperately" , "Powerfully desire" .)