He started to follow first ship away from the estuary (5)
I believe the answer is:
firth
'the estuary' is the definition.
(firth is a kind of estuary)
'he started to follow first ship away' is the wordplay.
'started' means to remove the last letter (I've seen 'starts' mean this).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'follow first' becomes 'f' (ist letter of 'follow').
'ship away' becomes 'irt' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'he' with its last letter taken off is 'h'.
'f'+'irt'='firt'
'h' after 'firt' is 'FIRTH'.
'from' is the link.
Can you help me to learn more?
(Other definitions for firth that I've seen before include "Arm of the sea - actor Colin" , "Scottish sea-inlet" , "Estuary" , "Narrow sea inlet in Scotland" , "Scottish river mouth" .)