Pirate queen and artist captured by Scottish engineer (5,3)
I believe the answer is:
water rat
'pirate' is the definition.
(water rat can mean a pirate)
'queen and artist captured by scottish engineer' is the wordplay.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'and' means one lot of letters go next to another.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'captured by' indicates putting letters inside.
'scottish engineer' becomes 'Watt' (James Watt, 18th-century inventor).
'er'+'ra'='erra'
'erra' inserted inside 'watt' is 'WATER RAT'.
(Other definitions for water rat that I've seen before include "Large semi-aquatic vole" , "Small amphibious rodent" , "boatman" , "swimmer" , "One employed by the bank" .)