Land covered currently by the engineers? (4)
I believe the answer is:
acre
'land' is the definition.
(I've seen this before)
'covered currently by the engineers?' is the wordplay.
'covered currently' becomes 'ac' (I can't justify this - if you can you should believe this answer much more).
'by' says to put letters next to each other.
'the engineers?' becomes 'RE' (abbreviation for Royal Engineers).
'ac'+'re'='ACRE'
Can you help me to learn more?
(Other definitions for acre that I've seen before include "A state of W Brazil" , "Not a lot of land" , "region of ground" , "Imperial land measure" , "Area measure - Israeli port - Brazilian state" .)