Old battleship from Aden at sea in dry period (11)
I believe the answer is:
dreadnought
'old battleship' is the definition.
(I've seen this before)
'aden at sea in dry period' is the wordplay.
'at sea' is an anagram indicator.
'in' is an insertion indicator.
'dry period' becomes 'drought' (I've seen this before).
'aden' is an anagram of 'eadn'.
'eadn' inserted into 'drought' is 'DREADNOUGHT'.
'from' acts as a link.
(Other definitions for dreadnought that I've seen before include "Old battleship" , "Early 20th-century class of battleship" , "(Class of) battleship launched in 1906" , "Revolutionary British battleship (1906) - first British nuclear-powered submarine (1963)" , "Old warship" .)