Rank nurse cuts pineapple (7)
I believe the answer is:
grenade
'pineapple' is the definition.
(pineapple can informally mean a grenade)
'rank nurse cuts' is the wordplay.
'rank' becomes 'grade' (grade is a kind of rank).
'nurse' becomes 'EN' (abbreviation for enrolled nurse).
'cuts' indicates putting letters inside (a group of letters 'cuts' into another word).
'grade' going around 'en' is 'GRENADE'.
(Other definitions for grenade that I've seen before include "Hand-thrown bomb" , "Small hand-bomb" , "Missile thrown" , "Angered (anag)" , "Handy bomb" .)