Geoff's beginning to wander in a small wood (5)
I believe the answer is:
grove
'small wood' is the definition.
(I've seen this in another clue)
'geoff's beginning to wander' is the wordplay.
'beginning to' suggests taking the first letters.
'wander' becomes 'rove' (synonyms).
The initial letter of 'geoff' is 'g'.
'g'+'rove'='GROVE'
'in a' is the link.
(Other definitions for grove that I've seen before include "Orchard" , "small plantation" , "Wood of small size" , "Group of trees or a small wood" , "Small wooded area" .)