For convenience, gets out of the National Front (5)
I believe the answer is:
gents
'for convenience' is the definition.
(I've seen this before)
'gets out of the national front' is the wordplay.
'out of' is an insertion indicator.
'front' indicates taking the first letters.
The initial letter of 'national' is 'n'.
'gets' enclosing 'n' is 'GENTS'.
(Other definitions for gents that I've seen before include "Men (colloq.)" , "Male loos" , "Public convenience" , "toilet" .)