Substantial recall of sex definitely heartless (4)
I believe the answer is:
tidy
'substantial' is the definition.
(thesaurus)
'recall of sex definitely heartless' is the wordplay.
'recall of' says the letters should be written backwards.
'sex' becomes 'it' (a common euphemism).
'heartless' suggests removing the centre.
'definitely' with its middle taken out is 'dy'.
'it' written backwards gives 'ti'.
'ti'+'dy'='TIDY'
(Other definitions for tidy that I've seen before include "Uncluttered" , "Clean and orderly" , "Neat - container for odds and ends" , "Set in order" , "Fairly big - orderly" .)