Insignificant guy's first to enter place for boats beside lake (8)
I believe the answer is:
marginal
'insignificant' is the definition.
(thesaurus)
'guy's first to enter place for boats beside lake' is the wordplay.
'guy's first' becomes 'g' (mst letter of 'guy').
'to enter' indicates putting letters inside.
'place for boats' becomes 'marina' (I can't explain this - if you can you should give a lot more credence to this answer).
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'lake' becomes 'L' (geographical abbreviation).
'g' put into 'marina' is 'margina'.
'margina'+'l'='MARGINAL'
Can you help me to learn more?
(Other definitions for marginal that I've seen before include "On the edges of" , "on border" , "Peripheral in alarming way" , "On the fringes" , "Very close (decision)" .)