Stride about on the ship when there's trouble (8)
I believe the answer is:
distress
'trouble' is the definition.
(I know that distress is a more specific form of the action the trouble)
'stride about on the ship' is the wordplay.
'about' is an anagram indicator.
'on' says to put letters next to each other.
'the ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'stride' with letters rearranged gives 'distre'.
'distre'+'ss'='DISTRESS'
'when there's' acts as a link.
(Other definitions for distress that I've seen before include "Misery" , "Affliction" , "Cause mental pain" , "Anguish - trouble - danger" , "Deep anxiety" .)