Another helping to wrap up old project (11)
I believe the answer is:
extrapolate
'project' is the definition.
(thesaurus)
'another helping to wrap up old' is the wordplay.
'another' becomes 'extra' (I've seen this before).
'helping' becomes 'plate'.
'to wrap up' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'plate' placed around 'o' is 'polate'.
'extra'+'polate'='EXTRAPOLATE'
(Other definitions for extrapolate that I've seen before include "forecast" , "Conclude from other data" , "Infer from what's known - to repeal tax (anag)" , "Infer further points from trends in data" .)