Small iceberg, one getting bigger outside loch (7)
I believe the answer is:
growler
'small iceberg' is the definition.
(term for a fragment of disintegrating iceberg)
'one getting bigger outside loch' is the wordplay.
'one getting bigger' becomes 'grower' (someone who is growing).
'outside' means one lot of letters goes inside another.
'loch' becomes 'l'.
'grower' placed around 'l' is 'GROWLER'.
(Other definitions for growler that I've seen before include "Iceberg" , "Unfriendly dog" , "Dog perhaps" , "Perhaps bear" .)