Long for introduction from Ricetti to enter grotto (5)
I believe the answer is:
crave
'long for' is the definition.
(I've seen this in another clue)
'introduction from ricetti to enter grotto' is the wordplay.
'introduction from' indicates taking the first letters.
'to enter' means one lot of letters goes inside another.
'grotto' becomes 'cave' (I've seen this before).
The initial letter of 'ricetti' is 'r'.
'r' put inside 'cave' is 'CRAVE'.
(Other definitions for crave that I've seen before include "Hunger for" , "Beseech" , "Feel a powerful desire for (something)" , "Desire strongly" , "Pine" .)