Reconstructed in Burma, extremely secure warship (9)
I believe the answer is:
submarine
'warship' is the definition.
(a submersible warship)
'reconstructed in burma extremely secure' is the wordplay.
'reconstructed' is an anagram indicator.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'secure' with its middle removed is 'se'.
'in'+'burma'+'se'='inburmase'
'inburmase' anagrammed gives 'SUBMARINE'.
(Other definitions for submarine that I've seen before include "Underwater (vessel)" , "Captain Nemo's Nautilus" , "... underwater craft" , "Under the sea" , "Submersible warship" .)