Poles initially expecting to be thin on the ground (6)
I believe the answer is:
sparse
'be thin on the ground' is the definition.
(I've seen this before)
'poles initially expecting' is the wordplay.
'poles' becomes 'spars' (spar is a kind of pole).
'initially' indicates taking the first letters.
The initial letter of 'expecting' is 'e'.
'spars'+'e'='SPARSE'
'to' is the link.
(Other definitions for sparse that I've seen before include "not packed together" , "Thinly scattered, not dense" , "Thinly-spread" , "Spares, being thin on the ground" , "rarely occurring" .)