Gather fuel blanketing heart of Ireland (5)
I believe the answer is:
pleat
'gather' is the definition.
(I've seen this before)
'fuel blanketing heart of ireland' is the wordplay.
'fuel' becomes 'peat' (peat is a kind of fuel).
'blanketing' means one lot of letters goes inside another (blanket can mean to surround).
'heart of' says to take the centre.
The central letter of 'ireland' is 'l'.
'peat' going around 'l' is 'PLEAT'.
(Other definitions for pleat that I've seen before include "Leapt (anag)" , "Gather" , "Tuck" , "that's tailor-made" , "work on skirt?" .)