English about to tuck into lean boneless meat (8)
I believe the answer is:
escalope
'boneless meat' is the definition.
'english about to tuck into lean' is the wordplay.
'english' becomes 'E' (abbreviation).
'about' becomes 'ca' (short for circa).
'to tuck into' indicates putting letters inside.
'lean' becomes 'slope' (sloping is a kind of leaning).
'ca' inserted inside 'slope' is 'scalope'.
'e'+'scalope'='ESCALOPE'
(Other definitions for escalope that I've seen before include "Thin piece of meat" , "what might feature in the catering" , "food" , "Cut of meat" , "Thin slice of boneless meat" .)