Sea bird nearly trapped in wild fen or swamp (6)
I believe the answer is:
engulf
'swamp' is the definition.
(I've seen this in another clue)
'sea bird nearly trapped in wild fen' is the wordplay.
'sea bird' becomes 'gull' (gull is a kind of sea bird).
'nearly' means to remove the last letter.
'trapped in' indicates putting letters inside.
'wild fen' becomes 'enf' (I can't explain this - if you can you should believe this answer much more).
'gull' with its final letter removed is 'gul'.
'gul' put inside 'enf' is 'ENGULF'.
'or' is the link.
Can you help me to learn more?
(Other definitions for engulf that I've seen before include "'Surround, overwhelm (6)'" , "Absorb, immerse" , "Swamp, overwhelm" , "Swallow up like wave" , "Flu gen (anag) - overwhelm" .)