Last of batsmen, positive around leg stump (7)
I believe the answer is:
nonplus
'stump' is the definition.
(thesaurus)
'last of batsmen positive around leg' is the wordplay.
'last of' says to take the final letters.
'positive' becomes 'plus' ('plus' can be similar in meaning to 'positive'**).
'around' means one lot of letters goes inside another.
'leg' becomes 'on' (cricket term, fielding positions).
The final letter of 'batsmen' is 'n'.
'n'+'plus'='nplus'
'nplus' going around 'on' is 'NONPLUS'.
(Other definitions for nonplus that I've seen before include "Throw into confusion" , "Surprise and confuse" , "Perplex totally" , "Perplex, confound" , "Get flummoxed" .)